air travel environmental impact

Air travel and climate change

What’s the problem with flying?

Flights are energy-intensive and depend on fossil fuels. Subsidies from fuel taxes give the airline industry an unfair advantage over other transportation modes. Consumers don’t see the true environmental costs of their air travel because low flight prices don’t reflect their environmental impact. Emissions from flights stay in the atmosphere and will warm it for several centuries. Because aircraft emissions are released high in the atmosphere, they have a potent climate impact, triggering chemical reactions and atmospheric effects that heat the planet.

A quarter of all emissions could be from flying by 2050

While many sectors are beginning to reduce their emissions, aviation’s have continued to grow. Carbon emissions from the airline industry grew by 75 per cent from 1990 to 2012. It’s expected they will continue to grow rapidly until 2050. If left unchecked, they could consume a full quarter of the available carbon budget for limiting temperature rise to 1.5 C.

Do new technologies make flying sustainable?

Requirements around biofuels and electrification could help. Because of battery weight, electrification fits for flights under 1,500 kilometres. That’s a problem since 80 per cent of flying is for flights longer than that.

Choose individual airlines carefully

Some airlines are taking voluntary steps to reduce carbon pollution. Choose airlines that have an efficient fleet and fly their planes with few empty seats. (Atmosfair.de has a ranking of emissions by airline.) Many airlines offer offsets to consumers. Some airlines that fly short distances, like B.C.’s Harbour Air, are switching to electric fleets.

Climate aviation facts

• One return flight from Montreal to London emits as much carbon emissions as heating a European home for an entire year.
• If the aviation sector were a nation, it would be among the top 10 global emitters. It is responsible for 12 per cent of transportation emissions.
• The global tourism industry is responsible for eight per cent of global emissions — more than the construction industry!
• Airline flying is going up five per cent a year but efficiency improvements have only increased by one to two per cent.
• Airline emissions make up a little more than three per cent of total emissions in Canada.
• The total carbon impact of a single flight is so high that avoiding just one trip can be equivalent to going (gasoline) car-free for a year.

Think twice before you grab that great flight deal for a weekend away in the sun. It’s not so great when you think about the emissions that will continue to warm the planet for centuries. Tom Green, climate policy analyst

What’s the best climate response to flying?

Go all the way.

Take a page from Greta Thunberg and the David Suzuki Foundation’s Gideon Forman and commit to stop flying altogether.

Take some steps

Fly only when necessary and stay longer. When flying for work, group meetings together. Take direct flights when possible. Or, skip the flight and use video teleconferencing.

Make a small change

If you must travel, offsets are a partial solution to lowering your impact.

Five ways to reduce your carbon footprint

Here are some meaningful decisions you can make to reduce your carbon footprint when you fly., fly economy.

Fly economy instead of business class to improve efficiency.

Take direct, non-stop flights

Take direct, non-stop flights to avoid high emissions during takeoff and landing.

Take daytime flights

Take daytime flights (due to heat-trapping effect of contrails and cirrus clouds at night, sunlight reflecting during day).

Choose airlines carefully

Choose airlines carefully. (Some airlines do a better job of ensuring they have a full passenger load and fly more efficient planes.)

Offset your flights

Buy Gold Standard carbon offsets.

What does bold climate action on aviation mean?

Changing the way the aviation industry operates will make a bigger climate impact than individual choices. The airline industry is not accountable for its climate impacts. The industry needs carbon-pricing regulations to drive down pollution.

Five actions you can take to hold industry accountable

Ask airlines to do their part.

Ask airlines whether they are buying carbon offsets themselves (not just offering them to you).

Demand more from the industry

Demand climate action from the International Civil Aviation Organization.

Make aviation accountable

Demand that international aviation be included under the Paris Agreement.

Elect climate-friendly governments

Elect politicians who are serious about reducing emissions and who have meaningful climate plans supported by science.

Price flying pollution

Demand that aviation industry regulators remove the unfair tax-free status of jet fuel for international flights and apply carbon pricing.

More you can do

Top 10 things you can do about climate change, are carbon offsets the answer to climate-altering flights, ten strategies every climate plan needs, join us on social.

Learn more about climate change and discover ways to take action

How Bad Is Air Travel for the Environment?

A large passenger jet may consume five gallons of fuel per mile traveled. Is it possible, then, that planes are more efficient than cars?

Alastair Bland

Wheels good, wings bad.

Environmental activists seem to bleat this mantra frequently in discussions about climate change, whether it’s a sustainable thing to travel and—if we must go anywhere at all—whether it’s better to fly or drive. It’s true that going anywhere via a combustion engine, or even an electric one , produces greenhouse gases. But how much worse, if at all, are the impacts of flying than those of driving? I’ve spent my week sifting through online information, processing data and crunching numbers, and the answer seems to be that flying can be significantly more efficient per traveler, per mile, than driving a car.

Dubious? Then put on your seatbelts, and let’s take a trip through statistic country. Let’s start with a look at the most famous of jets, the Boeing 747 . The Boeing website states that this model, with a gas tank capacity of 63,500 gallons, may burn five gallons of jet fuel per mile of flight . A 4,000-mile flight, then, requires 20,000 gallons of fuel. Divided among roughly 400 passengers , that’s 50 gallons of fuel to move each person aboard from, say, Chicago to London . A Honda Civic that gets 30 miles per gallon would need 133 gallons of fuel to make a trip of the same distance. Shared between two passengers (which may be a generous split; the average car carries 1.6 people in America), that would be 66.5 gallons per traveler. And an RV might move just seven miles on a gallon of gasoline. Split between the two people on board, that would be about 285 gallons of fuel each on a 4,000-mile tour. So far, air travel is looking to be more efficient.

If we keep studying this, the case for flying seems to build: According to FlightStats , an online air travel stat source, an average of 90,000 flights take off every day. The average flight distance is tough to determine, but this site calculated that the average distance of a medium-haul flight is 1,651 miles, so we’ll go with that (though many, many flights are probably 300-mile short hauls). At the 747 rate of five gallons per mile, that’ s 8,255 gallons burned per flight. And times 90,000 daily flights, that’s about 740 million gallons of fuel burned every day by airplanes—a very rough attempt at an estimate, but we get the idea.

Now for land travel: Americans alone reportedly drive 11 billion miles per day, according the Bureau of Transportation . A 2006 report (PDF) from the Environmental Defense Fund stated that Americans are responsible for 45 percent of the world’s vehicle emissions. That means we can roughly double—plus some—those 11 billion gallons per day to get the global total, which we’ll pin at 25 billion miles. If the average efficiency of a vehicle was as good as 25 miles per gallon ( wiki.answers says it’s more like 20 in America), then we can easily calculate that automobiles worldwide consume about one billion gallons of fuel per day.

The score: Automobiles, 1 billion gallons of fuel burned per day, airplanes 740 million. (But according to Carbonica , a carbon offset consultant for businesses, the discrepancy is much greater—and in favor of airplanes. Carbonica’s website states that whereas land transport accounts for 10 percent of carbon emissions , with personal vehicles the major component, commercial airplanes account for just 1.6 percent of emissions.)

Let’s do more math: Jet fuel produces 21 pounds of carbon dioxide emissions per gallon burned. (How is that possible, you ask, if a gallon of fuel weighs less than seven pounds? When hydrocarbon molecules separate through combustion, the carbon atoms recombine with two clunky oxygen atoms each, accounting for substantial weight gain.) And gasoline produces almost 20 pounds of carbon dioxide emissions per gallon burned. About the same for each, meaning that we get more emissions globally from cars than we do from airplanes.

Now, let’s look at this from another angle and see if the results look similar: Airplanes measure fuel efficiency by how far one seat can travel per gallon, and, according to Department of Transportation data reported in the Wall Street Journal , major U.S. airlines average 64 seat miles per gallon. Let’s say again that the average American car moves 25 miles per gallon, with each car carrying, on average, 1.6 people . Translated into airline units, that’s 40 seat miles per gallon for a car. Airplanes, it still appears, are more efficient than cars.

Some sources report very different conclusions than mine. For example, this article from the U.K.-based Environmental Transport Association reports flying to be about three times more carbon costly than driving . But they came to this conclusion because their calculations are based on an extremely short-haul flight of 185 miles (Manchester to London, one-way) and a very efficient car. Because so much fuel is incinerated during an airplane’s takeoff , the longer the flight, the more efficient it is (though only to a point, due to the fact that it takes fuel to carry fuel , and fuel is heavy; the “ sweet spot ” for airplane efficiency seems to be about 4,500 miles).

Obviously, the more people that can be crammed onto an airplane, the less ownership each individual has in the fumes that it leaves behind. Thus, one obvious fault of the aviation industry is the fact that an airplane, even if just a handful of seats are sold, must still make the scheduled flight: When I flew from Auckland, New Zealand, to San Francisco in February, every passenger on board had room to lie down. In a perfect world, that flight would have been canceled.

Before you walk away thinking flying is greener than driving, consider some key points. First, airplanes emit their fumes directly into the upper atmosphere, where they may linger longer and cause more damage than the same gases at lower altitudes. Second, air travel is not a service that very often takes us places that we really need to be. That is, the Boston businessman that flies once a week to Miami for meetings would not be using a car to make the same journey if airplanes didn’t exist. He might simply not go at all. (Though in a better world, Americans might enjoy a high-speed rail system. Consider, Europe, home of the TGV ; and Japan, where the magnetic levitation train seems almost a trick of magic, moving nearly as fast as an airplane on virtually no fuel. One of the most reliable “high-speed” train corridors in America, according to this article , is the one between Boston and D.C., served by an iron horse that clunks along at 70 miles per hour.) And the cyclist that flies from Seattle to Lisbon for a two-month bicycle tour of Europe might simply never go at all if it required taking a multiweek boat trip just to get to the starting point. She might, instead, explore the Cascades and the Rockies—not a bad alternative. (But this group of musicians— the Ginger Ninjas, which I featured several months ago —has toured in Europe by bicycle after traveling there by boat.) In this sense, flying is bad since it is not replacing another means of transport; it is simply offering the world’s wealthy another travel option. It is a luxury.

What’s more, the airline industry is growing. According to this post in the Guardian ‘s “Travel Blog,” air travel may not be a big contributor to carbon emissions, but it’s been among the fastest-growing causes of global warming for years, with the industry expanding at 5 percent annually . And with the world’s most populous country now becoming among the wealthiest, hundreds of millions of Chinese citizens may soon enter the ranks of the frequent flier, as predicted by Boeing , which expects its passenger traffic to triple by 2030—with most of that growth occurring in China.

Drawing a single conclusion from this discussion isn’t easy, given the many variables, like a plane’s seating capacity, its fuel load, the flight distance and the number of passengers on board. But there is one statement you’d have trouble arguing with: If you hope to visit Hawaii this fall, you should probably fly.

Wings good, wheels good—propeller simply awful: If you think a Boeing 747 is inefficient at five gallons to the mile, then try to swallow this: The Queen Elizabeth II moves 29 feet per gallon . That’s 200 gallons of fuel burned per nautical mile. But the cruise ship, retired as of 2008 , could carry as many as 1,777 passengers, plus another 1,040 crew members. Now that’s a boat in the carpool lane.

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Alastair Bland | | READ MORE

Alastair Bland is a journalist based in San Francisco who writes about the environment, agriculture, science and food.

Opportunities for industry leaders as new travelers take to the skies

Travel fell sharply during the COVID-19 pandemic—airline revenues dropped by 60 percent in 2020, and air travel and tourism are not expected to return to 2019 levels before 2024. 1 “ Back to the future? Airline sector poised for change post-COVID-19 ,” McKinsey, April 2, 2021; “ What will it take to go from ‘travel shock’ to surge? ” McKinsey, November 23, 2021. While this downturn is worrisome, it is likely to be temporary. McKinsey’s latest survey of more than 5,500 air travelers around the world shows that the aviation industry faces an even bigger challenge: sustainability.

The survey results indicate emerging trends in passenger priorities:

About the survey

We asked about 5,500 people in 13 countries, half of them women, to answer 36 questions in July 2021. Each had taken one or more flights in the previous 12 months. More than 25 percent took at least half of their flights for business reasons; 5 percent had taken more than eight flights in the previous 24 months. They ranged in age from 18 to over 75 and hailed from the US and Canada, the UK, Sweden, Spain, Poland, Germany, Saudi Arabia, India, China, Japan, Australia, and Brazil.

Topics included concerns about climate change and carbon emissions, carbon reduction measures, and factors influencing tourism stays and activities.

We compared the results to those of a survey asking the same questions that we conducted in July 2019.

• Most passengers understand that aviation has a significant impact on the environment. Emissions are now the top concern of respondents in 11 of the 13 countries polled, up from four in the 2019 survey. More than half of respondents said they’re “really worried” about climate change, and that aviation should become carbon neutral in the future.
• Travelers continue to prioritize price and connections over sustainability in booking decisions, for now. This may be partly because no airline has built a business system or brand promise on sustainability. Also, some consumers may currently be less concerned about their own impact because they’re flying less frequently in the pandemic. That said, almost 40 percent of travelers globally are now willing to pay at least two percent more for carbon-neutral tickets, or about $20 for a $1,000 round-trip, and 36 percent plan to fly less to reduce their climate impact.
• Attitudes and preferences vary widely among countries and customer segments. Around 60 percent of travelers in Spain are willing to pay more for carbon-neutral flights, for example, compared to nine percent in India and two percent in Japan.

This article outlines steps that airlines, airports, and their suppliers could take to respond to changing attitudes and preferences. The survey findings suggest that airlines may need to begin with gaining a deeper understanding of changes across heterogenous customer segments and geographies. With those insights in hand, they could tailor their communications, products, and services to differentiate their brands, build awareness among each passenger segment, and better connect with customers.

Would you like to learn more about our Travel, Logistics & Infrastructure Practice ?

The survey findings point to fundamental and ongoing changes in consumer behavior.

After a decade of steady growth in passenger traffic, air travel was hit hard by the pandemic. International air travel immediately fell by almost 100 percent, and overall bookings declined by more than 60 percent for 2020, according to Airports Council International. At the time of writing, revenue passenger miles have returned to close to pre-pandemic levels in the United States, but still lag behind in other markets. 2 “COVID-19: October 2021 traffic data,” International Air Transport Association (IATA), December 8, 2021. In its October 2021 report, before the Omicron variant emerged, the International Air Transport Association (IATA) forecast that the industry’s losses would be around $52 billion in 2021 and $12 billion in 2022. 3 “Economic performance of the airline industry,” IATA, October 4, 2021.

Furthermore, travelers’ preferences and behaviors have changed sharply during the pandemic, particularly around health and safety requirements. An Ipsos survey for the World Economic Forum found that, on average, three in four adults across 28 countries agreed that COVID-19 vaccine passports should be required of travelers to enter their country and that they would be effective in making travel and large events safe. 4 “Global public backs COVID-19 vaccine passports for international travel,” Ipsos, April 28, 2021. And a 2021 survey by Expedia Group found that people buying plane tickets now care more about health, safety, and flexibility than previously. But, there is also renewed interest in travel as nearly one in five travelers expected travel to be the thing they spent the most on in 2021, one in three had larger travel budgets for the year, and many were looking for new experiences such as once-in-a-lifetime trips. 5 “New research: How travelers are making decisions for the second half of 2021,” Skift, August 26, 2021.

Comparing McKinsey’s 2019 and 2021 survey results, sustainability remains a priority as respondents show similar levels of concern about climate change, continue to believe that aviation must become carbon neutral, and want their governments to step in to reduce airline emissions. Some changes were more striking. The share of respondents who say they plan to fly less to minimize their environmental impact rose five percentage points to 36 percent. In 2021 half of all respondents said they want to fly less after the pandemic. Changes in opinion varied across markets. Passengers in the UK, US, and Saudi Arabia, for example, were more likely to feel “flygskam,” (shame about flying) while those in Spain, Poland, and Australia felt significantly less guilty about flying.

It is worth tracking these trends in each market and demographic, because passengers’ experiences and opinions are increasingly relevant: passengers spend far more time online, increasingly trust each other’s recommendations more than traditional marketing, and can reshape brand perceptions faster than ever. 6 “ Understanding the ever-evolving, always-surprising consumer ,” McKinsey, August 31, 2021. In some markets consumers may reward airlines that meet rising demands for environmental sustainability—and punish those who fall behind.

The Australian airline Qantas may be acting on a similar belief. In November 2021, it announced a new “green tier” in its loyalty program. The initiative, based on feedback from passengers, is “designed to encourage, and recognize the airline’s 13 million frequent flyers for doing things like offsetting their flights, staying in eco-hotels, walking to work, and installing solar panels at home”. Qantas states that it is one of the largest private-sector buyers of Australian carbon credits, and it will use program funds to support more conservation and environmental projects. 7 “Qantas frequent flyers to be rewarded for being sustainable,” Qantas media release, November 26,, 2021. “A look at how people around the world view climate change,” Pew Research April 18, 2019. Washington Post-Kaiser Family Foundation climate change survey, July 9 to August 5, 2019.

Given these shifting trends, it may be helpful for all industry stakeholders to maintain a deep and up-to-date understanding of consumer segments in each market that they serve. Three main findings about today’s travelers emerged from the 2021 survey:

Finding 1: Most travelers now have concerns about climate change and carbon emissions—and many are prepared to act on these concerns

Concern about carbon emissions from aviation did not rise much during the pandemic, probably in part because air travel declined so sharply. About 56 percent of respondents said they were worried about climate change, and 54 percent said aviation should “definitely become carbon neutral” in the future.

While these numbers have increased only one or two percentage points since 2019, the share of respondents who rank CO 2 emissions as their top concern about aviation—ahead of concerns such as noise pollution and mass tourism—rose by nine percentage points to 34 percent. More than 30 percent of respondents have paid to offset their CO2 emissions from air travel.

Finding 2: Price and connections still matter much more than emissions to most travelers

Of the nine major factors travelers consider when booking a flight, carbon emissions consistently rank as sixth-most important across customer segments. This may be partly because most airline marketing centers around low cost or superior service, and pricing and revenue management are targeted at price and best connection. Most booking websites allow prospective travelers to sort by price and number of connections, for example, but not by carbon footprint. Google Flights has made a first step, showing average CO2 emissions per flight and improving transparency for travelers.

Travelers might begin to make different choices if emissions featured more prominently in the booking process—particularly if more airlines offered CO 2 reduction measures that delivered genuine environmental impact.

Finding 3: Attitudes vary widely by demographics and geography

Beliefs about the seriousness of climate change, and how to respond to it, vary across demographics and geographies (exhibit). Although younger people are generally more aware of the predicted consequences of climate change, older cohorts have become more concerned about climate change since the 2019 survey. In some countries, large majorities see climate change as a major threat, while that represents a minority view in other countries.

The survey shows that frequent travelers feel slightly more shame about flying than other respondents—37 percent compared to 30 percent—but show a much lower intention to reduce their air travel to minimize their climate impact, at 19 percent compared to 38 percent.

According to Pew Research, more than 80 percent of people in Greece, Spain, France, and South Korea believe climate change is a major threat, compared to around 40 percent of those in Russia, Nigeria, and Israel. 8 “A look at how people around the world view climate change,” Pew Research April 18, 2019. According to 2019 polling by the Washington Post and Kaiser Family Foundation, more than three-quarters of Americans believe it represents a major problem or a crisis—but fewer than half are willing to pay to help address it. 9 Washington Post-Kaiser Family Foundation climate change survey, July 9 to August 5, 2019.

These numbers may change quickly in the next few years as discussions about climate change become less abstract as oceans rise and storms, forest fires, and droughts become more severe. Instead of being one topic of concern among many, millions more people around the world may come to see climate change as today’s greatest challenge.

This shift seems to be apparent in government action, especially in mature economies. The US, for example, announced its intention to exit the Paris Agreement in June 2017 but pledged to rejoin in April 2021. 10 “Climate change: US formally withdraws from Paris agreement,” BBC, November 4, 2020; “President Biden sets 2030 greenhouse gas pollution reduction target,” White House fact sheet, April 22, 2021. And in September, the White House set a goal for the country to produce 3 billion gallons of sustainable aircraft fuel annually by 2030—up from about 4.5 million gallons produced in the US in 2020—which would cut carbon emissions from flying by 20 percent compared with taking no action. 11 “Biden administration advances the future of sustainable fuels in American aviation,” White House fact sheet, September 9, 2021.

Taking stock of the pandemic’s impact on global aviation

How the industry can be cleared for takeoff.

Travelers’ attitudes and behaviors appear to be in flux, and will likely continue to change. Depending on the world’s progress in preventing and treating COVID-19, the industry will likely take at least a couple of years to recover from the downdrafts caused by the pandemic.

In this unique moment in aviation history, airlines may be able to communicate in new ways to inspire passengers to join the fight against climate change. Based on McKinsey’s experience in aviation and other industries around the world, there may be an opportunity for carriers to make it “easy to do good”. When following such an approach, experience shows that customers are drawn to straightforward language, demonstrations of what the industry is doing in this area, and the tangible benefits of those efforts. The most compelling stories are positive and connect with customers’ emotional needs.

As in the early days of travel advertising, airlines could reinforce the idea that the journey is the destination—that “getting there is half the fun.” By inviting customers to get involved in creating a greener future and own the solution, they could forge new partnerships and deepen loyalty.

Actual progress will be essential; organizations that talk about sustainability without demonstrating action may quickly be held to account. Simply keeping pace with trends or regulatory requirements will offer no advantages. Airlines that move boldly, such as by replacing rather than modifying a loyalty program with some kind of “planet-positive” scheme, will stand out from competitors.

The survey results and McKinsey’s work in the industry lead us to believe that the market is ready for a forward-thinking airline to chart a route to a cleaner future for the industry. Leading airlines that build a business strategy and brand promise on sustainability will likely attract a growing share of business and leisure travelers, fresh capital and talent, and new allies across the industry, government, and society at large.

In the years ahead, more customers will be willing to pay for sustainability, particularly if airlines can engage them with interesting approaches, such as gamification in frequent flyer programs, opt-out rather than opt-in offsets, “green fast lanes” for check-ins and security control, and customized emission-reduction offers. Decarbonization could become the standard to reach and maintain next-tier levels in loyalty programs. Passengers will be able to join the global decarbonization team and transform flight shame into flight pride.

Like many private flyers, corporate customers will look for ways to mitigate their CO 2 footprint. Passenger and cargo airlines could craft attractive decarbonization programs to engage the rising numbers of corporates aiming to significantly reduce their scope 3 emissions from air transport.

No single set of approaches will be effective in every geography or with every passenger segment. But airlines with a deep understanding of their customers’ changing needs and desires will continue to outperform those that don’t. Such organizations could recruit more of their passengers to the decarbonization team while protecting their brands, the future of aviation, and the planet itself.

Mishal Ahmad is a manager in McKinsey’s New Jersey office, Frederik Franz is a senior associate in the Berlin office, Tomas Nauclér is a senior partner the Stockholm office, and Daniel Riefer is an associate partner in the Munich office.

The authors would like to thank Joost Krämer for his contributions to this article.

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Sustainability

Airlines want to make flight more sustainable. how will they do it, air travel produces millions of metric tons of carbon dioxide each year. new technologies could help airlines reduce their emissions and meet their sustainability goals, by leigh krietsch boerner, september 3, 2021 | a version of this story appeared in volume 99, issue 32.

Credit: Chris Gash

• How can companies recycle wind turbine blades?
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• Industrial ammonia production emits more CO 2 than any other chemical-making reaction. Chemists want to change that
• EPA designates PFOA and PFOS as hazardous substances
• Lithium-ion battery recycling goes large

AIRLINES WANT TO GO GREEN

Shrinking jet fuel's carbon footprint

The search for greener airplane materials, supersonic flight's sustainability challenge.

Air travel produces about 3% of global carbon dioxide emissions, and it is one of the fastest-growing sources of greenhouse gases, according to the International Council on Clean Transportation (ICCT). “The least-emitting flight is one that doesn’t happen at all,” says Nikita Pavlenko , senior fuels researcher for the ICCT. This advice is not practical for people who need to travel long distances or for the airline industry. But climate scientists say that to get climate change under control, airlines need to reduce their emissions.

Multiple airline companies have announced programs to try to become more sustainable in the coming years. Delta Air Lines recently committed $1 billion to become carbon neutral by 2030. JetBlue pledged to get there by 2040, and United Airlines by 2050 . Many other global airlines around the world have made similar promises.

But making air travel more sustainable is not simple. It takes a lot of energy to lift people and cargo into the air and carry them long distances. Airlines are trying to reduce their emissions in several ways. Probably the most common is switching from traditional fossil-derived jet fuels to ones that are made from renewable sources and have lower emissions during production. Airlines are also looking to new materials and coating technologies to make planes lighter, more aerodynamic, and more resistant to wear and tear. Meanwhile, a few airlines, such as United, think they can get to carbon neutrality while reintroducing supersonic flight.

Read on to learn more about the problems companies will face when trying to make their planes more environmentally friendly, as well as the technologies they may employ.

Emissions from burning jet fuel make up a large portion of commercial airlines’ environmental impact. Airlines are looking to reduce this with alternative fuels

When airline executives think about how to make air travel more sustainable, the biggest arrow points to the fuel burned to keep planes in the air. "For short-haul flights, there's some encouraging movement for zero-emission planes, such as those running on electricity," Pavlenko says. "But for everything else, it comes down to what fuel you can switch to."

The goal of using sustainable aviation fuels, or SAFs, is to reduce the amount of greenhouse gases emitted during the lifetime of the fuels, from production to combustion, compared with current petroleum-based jet fuels. The scale of that reduction depends on the process used to make the fuel and the carbon source. And even though some SAFs boast significant emission reductions, few are made at large scale.

Pathway to Fischer-Tropsch synthetic paraffinic kerosenes

To make Fischer-Tropsch synthetic paraffinic kerosenes, industrial chemists oxidize the carbon source to synthesis gas, a mixture of carbon monoxide and hydrogen, and then run this gas over an iron, cobalt, or ruthenium catalyst to produce hydrocarbons. They then blend the products with fossil-derived jet fuels before the result can be burned in a jet engine.

Sources: International Council on Clean Transportation, National Energy Technology Laboratory Note : In the Fischer-Tropsch reaction scheme, n indicates the number of carbons in the resulting hydrocarbons. For sustainable aviation fuels, that number is usually between 10 and 20.

Generally, commercial airliners use kerosene fuels called Jet A and Jet A-1. They're mixtures of paraffins, naphthenes, aromatics, and olefins and are mostly derived from petroleum. Some companies, such as Airbus, which declined to be interviewed for this story, are looking to hydrogen as a fuel, since it combusts to produce water vapor. But developing H 2 -burning engines is in early stages, so such planes are still far in the future.

Most companies are looking instead at drop-in fuels, or fuels that can work with existing jet engines. They need to have similar properties to jet fuel, including their energy released when burned, performance at low temperatures, and flow. These specifications ensure that the fuels will behave the same way fossil-derived jet fuel does in an airplane's engine, Pavlenko says. One way fuel manufacturers get SAFs to match these specifications is by blending them with conventional jet fuel, he says. How much is blended varies quite a bit, however. Most SAFs need to be blended 50:50 with Jet A-1. And while there's interest in SAFs that don't need to be blended, none have been commercially approved, according to Pavlenko. The standards these 100% SAF fuels would have to meet haven't even been set yet and will take probably 3–5 years to get completed, Rick Barraza, vice president of administration at the alternative-fuel company Fulcrum BioEnergy , says in an email.

There are three main ways to make SAFs: from hydroprocessed esters and fatty acids (HEFA), Fischer-Tropsch synthetic paraffinic kerosene (FT-SPK), and alcohol-to-jet synthetic paraffinic kerosene (ATJ-SPK). All three can be used at similar blend levels, around 50%.

To make HEFA fuels, industrial scientists remove the oxygens from molecules in unused vegetable oils, or waste fats, oils, and greases. Then they treat the mixtures with hydrogen to yield burnable hydrocarbons the right length for jet fuel, usually between 10 and 20 carbons long, according to the ICCT. Compared with Jet A and Jet A-1, these fuels are the most cost competitive SAF technology, Pavlenko says.

To make Fischer-Tropsch-SPK, scientists oxidize a wide variety of plant and human wastes and residues to make synthesis gas, a mixture of H 2 and carbon monoxide. Adding a catalyst—usually iron, cobalt, or ruthenium—to this gas triggers Fischer-Tropsch synthesis, which produces hydrocarbons.

The sources for alcohol-to-jet-SPK are crops such as sugarcane and corn, plant and agriculture wastes, and in some cases industrial flue gases. Generally, scientists convert these feedstocks to ethanol or isobutyl alcohol and then upgrade the alcohols to long-chain kerosene by removing water, treating them with hydrogen, and combining short-chain hydrocarbons to form longer ones.

Fickle fuels

Depending on the carbon source, sustainable aviation fuels can produce a large range of greenhouse gases over their lifetimes. Scientists compare these fuels’ carbon footprints by looking at the life-cycle carbon intensity, measured in grams of CO 2 equivalent (g CO 2 e) released per megajoule of energy burned.

Sources: International Council on Clean Transportation, International Civil Aviation Organization. a Not including plastic municipal solid waste.

These three alternative fuels don't have the same impact on the environment. The ICCT recently released a report showing the amount of greenhouse gases emitted during various alternative fuels' life cycles, including growing or collecting the carbon sources, synthesizing the fuels, and combusting them in an engine. The data came from the International Civil Aviation Organization 's Carbon Offsetting and Reduction Scheme for International Aviation program , a United Nations effort.

The ICCT found that alcohol-to-jet-SPK fuels tend to have higher emissions than HEFA or Fischer-Tropsch-SPK fuels because making alcohols from starch-based crops takes a lot of energy and emits substantial amounts of greenhouse gases. In general, biofuels made from wastes and by-products tend to have lower greenhouse gas emissions than crop-based ones, the ICCT's Pavlenko says.

The SAF industry is shifting more to such waste-based fuels, according to Aaron Robinson , senior manager of environmental strategy and sustainability for United Airlines. Ten years ago, alternative-fuel companies focused on growing crops for biofuels. "Two out of our first three SAF flights were powered by agriculturally grown material," he says. "That's the way we thought the industry was going to be going." But life-cycle analyses have shown how environmentally costly that route can be. When the fuel source is a food crop, the process contributes to deforestation because more land is needed to grow the additional crops, Pavlenko says.

No fuel companies currently produce Fischer-Tropsch-SPKs, so the fuel currently in production with the lowest lifetime GHG emissions is HEFA, depending on the feedstocks. "Some SAFs actually don't offer very many, if any, greenhouse gas savings at all, such as palm oil–derived biofuel, whereas others can have greenhouse gas reductions approaching 100%," Pavlenko says. Used cooking oil and waste animal fats have lower lifetime emissions and are more popular than palm oil, he says.

The company closest to commercial production of Fischer-Tropsch-SPKs is Fulcrum BioEnergy in Pleasanton, California. This company's technology uses municipal solid waste, also known as trash, to make jet fuel. Fulcrum plans to start producing biofuel in the last quarter of this year at its plant just east of Reno, Nevada, Vice President Barraza says. The company plans to build eight other plants with a total production of about 1.5 billion L per year, enough to meet the needs of United and other partners, which include Cathay Pacific Airways and Japan Airlines, Barraza says.

Using municipal solid waste as a feedstock for jet fuel could provide significant greenhouse gas emission savings. Generally, the breakdown of municipal solid waste in landfills produces methane, which has over 28 times the climate change impact of CO 2 over 100 years. "By diverting [municipal solid waste] away from the landfill, we are thereby avoiding all that methane from being generated," Barraza says. The overall greenhouse gas life-cycle analysis for municipal solid waste fuel shows that this pathway can reduce greenhouse gas emissions by over 85% compared with fossil fuels. But the key is the company must first remove plastic waste from the trash.

Plastic sitting in a landfill is actually a form of carbon storage, the ICCT's Pavlenko says. "But if you're converting it into fuel and combusting it, that carbon that would have been safely in the ground for a long time, now it's in the atmosphere," he says. Barraza says the waste feedstock the company uses is mostly organic or biogenic material. "We have the ability to remove a fair amount of the high-value plastics and metals from the raw MSW as part of our feedstock preparation process," he says.

Powering airplanes with waste is certainly the dream for sustainable flight, and a viable one, United's Robinson says. "You could power all of United using just 20% of US landfill waste."

But the reality is that relative to total amounts of jet fuel, airlines aren't using a lot of SAFs right now. "It's less than 0.1% globally," Pavlenko says. For example, United has used about 3.8 million L of SAFs per year in recent years, compared with more than 15 billion L per year of conventional jet fuel, Robinson says. To bump up the amount of SAFs it has access to, United has struck deals with Fulcrum and World Energy , he says. Delta and JetBlue have agreements to purchase SAFs from the Finnish company Neste . These agreements give airlines both price and source certainty for future fuels and provide the fuel companies with a future market for their products.

Fulcrum's Barraza declines to provide details about the timeline for delivering the fuel the firm has promised to United. The big question, Robinson says, is how much the fuel is going to cost and if United can get it soon enough to make a difference in lowering emissions.

New materials could help airlines go green Companies and researchers are investigating new composites and coatings that are lighter, thinner, and more environmentally friendly than today’s

The materials used in every part of a plane can determine its weight, aerodynamics, and resistance to the wear and tear of whooshing through the atmosphere. What these materials, and the coatings applied to them, are made of and how they perform can therefore significantly affect a plane's environmental impact. Companies and researchers are now investigating lighter and less toxic materials and coatings for the more sustainable planes of the future.

Airplane coatings

Every part of a plane needs a coating to improve its function. Here are some examples from outside and inside a plane.

1. Cockpit windows: In addition to heat- and ultraviolet-resistant coatings, cockpit windows are coated with a conductive oxide material. Pilots can apply a voltage to the material to melt ice off the windows, saving deicing time and reducing delays.

2. Engines: The combustion chamber of a jet engine can reach almost 1,400 °C, and newer, more efficient engines need even higher fuel compression and combustion temperatures. All parts of airplane engines are coated with materials, often ceramics, to help them withstand these extremes.

3. Fuselage: The outsides of planes need coatings such as chrome to help resist rust, and polyurethanes and acrylics to protect against damage from ultraviolet light and improve aerodynamics. Coatings are also used to add airline logos to planes.

4. Passenger windows: Windows get coatings made from plastics and stretched acrylics to make them heat and ultraviolet resistant. New technology in development could add an electrochromic layer. That would allow passengers to dim the windows, eliminating the need for window shades.

5. Landing gear: Protection against rust and impact resistance are especially important in the landing gear, critical parts of the aircraft that have to withstand harsh conditions and intense forces. Coatings for landing gear include chrome; hard, diamond-like carbon; and anodized metals.

6. Passenger seats: Parts inside the plane that passengers don’t see, such as the mechanism that lets passengers recline their seats, also need coatings to help them resist friction and wear.

7. Tray tables: Plastic tray tables get coatings to prevent food stains, kill viruses and bacteria, and resist damage from cleaners used 10–15 times a day. These polymer materials have embedded nanoparticles or are treated with nonstick coatings and quaternary ammonium compounds.

An airplane's weight significantly contributes to its carbon footprint because lighter aircraft need less fuel to operate, and less fuel burned means lower emissions. One way to make airplanes lighter is to change what they're made of.

Airplanes were historically made of metal, usually an aluminum alloy. Now some new airplanes, such as the Boeing 787 and Airbus A350, are about 55% composite materials instead, says Samit Roy , an aerospace engineer at the University of Alabama. A composite is anything made up of two or more materials. For example, some companies build aircraft wings, tails, and parts of the fuselage with polymers that have embedded carbon or glass fibers. Composites can reduce the weight of airplanes by up to 20%, Roy says.

Roy's group is working on new composites consisting of carbon fiber with embedded nanoparticles. In addition to being lightweight, these materials can be 3D printed. Printing would reduce material loss because parts can be produced in the exact size and shape needed instead of being cut out from a larger piece of material, as is done with aluminum, Roy says.

Roy and colleagues also want to make these composites conductive. "If an aluminum aircraft like a 747 gets struck by lightning, the lightning passes right through on the skin of the aircraft, doing minimal or no damage," Roy says. But most composite materials used in aircraft are not conductive on their own, so a direct zap could do serious damage. To protect against this, aircraft manufacturers like Boeing and Airbus put copper mesh over the fuselage of their composite planes, but that layer adds cost and weight, Roy says. To improve electrical conductivity and let planes ditch the heavy copper layer, scientists are developing reinforced composites with nanographene or carbon nanotubes, and conductive polymers.

Coatings' main purpose is to add new functions and properties to surfaces, says Lars Haubold , manager for coating technology at the diamonds and coatings division of Fraunhofer USA Center Midwest , a research nonprofit that is partnered with Michigan State University. Coatings provide corrosion protection, add insulation, reduce air friction, or simply decorate the plane with a company's logo. Pretty much every part of a commercial airplane gets some kind of coating, whether it's the windows to add ultraviolet light protection, the landing gear to keep the mechanics from rusting, or the tray tables to make them stain resistant.

One of the primary jobs of some coatings is to keep a part from rusting and breaking down. For many years, the go-to corrosion inhibitor in airline industry coatings was hexavalent chromium, also called chrome. Unfortunately, the compound is a known carcinogen and is harmful to the eyes, skin, and respiratory system. Cr(VI) has contaminated water supplies in a few well-known cases, such as the one featured in the movie Erin Brockovich . Because of Cr(VI)'s health and environmental issues, the US Environmental Protection Agency limits chromium emissions in electroplating and levels in drinking water . The US Occupational Safety and Health Administration also lists the compound as a carcinogen and regulates workers' exposure to it.

Coatings companies have been trying to eliminate the compound for a very long time, says Robin Peffer, the global marketing manager for aerospace coatings at the paint and coatings company PPG Industries . The company is looking to alternatives with alkali earth, rare earth, and transition-metal compounds. In addition to being less toxic, chrome-free materials can potentially be lighter. "So if we have a primer that's 20 or 30% lighter than standard chromated primers today, that's going to have a direct impact on fuel efficiency for the aircraft," Peffer says.

Changing the way coatings get applied is another way to improve sustainability. Chrome-based coatings typically need to be sprayed on, Peffer says. Many of the alternative anticorrosion coatings can be applied by immersing the parts in a coating solution instead. This process allows coatings companies to apply the material more efficiently, especially to complex shapes. "We can get upwards of 75% or more weight savings because we're putting the coating on more uniformly across the part than we can with spray," Peffer says.

Plasma electrolytic oxidation is another potential way to apply coatings. This method is similar to anodizing, which electrochemically converts a metal to its oxide, making it more durable and corrosion resistant. In plasma electrolytic oxidation, scientists apply between 200 and 1,000 V to a metal submersed in a coating solution, heating the material up to its plasma state, around 10,000 °C, says Ankit Khurana, vice president for engineering at Keronite , a start-up surface technology company. The material's lattice structure then opens up, allowing the material to be infused with particles from the surrounding solution. This process embeds the coating material into the metal while it converts into an oxide layer, he says.

The resulting layer is both thinner and harder than one created by traditional anodizing, Keronite CEO Matt Hamblin says. "The coatings are anywhere from 5 to 35 μm thick, so they really carry no weight at all," he says.

Plasma electrolytic oxidation coatings also are three to four times as wear resistant, so they can be replaced less frequently, Hamblin says. Commercial airliners fly an average 3,500 h per year, so their coatings need to be replaced at regular intervals, some as often as every 3 months. A longer-lasting coating means less time in the repair hangar and less overall material used, Hamblin says, providing both cost savings for the airline and improved sustainability.

One thing to keep in mind, Hamblin says, is that a lot of these technologies are going into airplanes currently being designed that will be flying years from now, not what's currently in the air. Airline companies have "a tendency to redesign or reuse what they've already got, maybe with a slight tweak," he says. "You don't necessarily see these huge shifts." And because airlines use their planes for a long time, current coating technologies will probably still be used on planes in the air for the next 25 years.

The University of Alabama's Roy agrees that these technologies will find commercial use down the road. "That's what research is all about, the look ahead," he says. But as time goes on, more and more airline companies and science agencies are becoming aware of how important sustainable materials technology is, Roy says. "I think now they're waking up more to it. The possibility."

Airplane start-up Boom Supersonic claims its planes can achieve net-zero carbon emissions. Critics aren’t so sure

Supersonic air travel has had a mixed record of success. Operating from 1976 to 2003, the Concorde could fly between London and New York City in around 3 h and was considered a marvel of aerospace engineering. But the plane was retired because both airlines that operated the flights, Air France and British Airways, were losing money on the supersonic routes.

Gas guzzler

According to a 2018 study by the International Council on Clean Transportation, the average supersonic airplane would burn between five and seven times the fuel per passenger that a conventional, subsonic flight on the same routes does.

Source: Anastasia Kharina, Tim MacDonald, Dan Rutherford, Environmental Performance of Emerging Supersonic Transport , The International Council on Clean Transportation, July 17, 2018. Note: Fuel estimates are averages and vary depending on aircraft specifications and environmental policies.

Since then, supersonic airline companies have popped up and petered out. One new company, though, is getting attention for its sustainability goals. Boom Supersonic , an aircraft start-up based in Denver, made headlines in June when United Airlines agreed to buy 15 of its supersonic Overture airplanes, with an option to buy 35 more. Both Boom and United have highlighted the deal as helping United meet its sustainability initiative to reach net-zero carbon emissions by 2050. In numerous press releases, Boom has announced that Overture is "expected to be the first large commercial aircraft to be net-zero carbon from day one, optimized to run on 100% sustainable aviation fuel." Boom has rarely spoken to the press about the details of its sustainability plans and declined to be interviewed for this story.

Critics, however, aren't so sure about the company's sustainability claims. Supersonic flight would have to overcome some significant obstacles to become both sustainable and financially viable. Here is a look at some of those hurdles.

Disclosure: The author has a relative that works at an airline not mentioned in the story.

Rise in CO 2

If supersonic planes join worldwide fleets, they could increase carbon dioxide emissions from air travel by approximately 10% in 2035.

Global CO 2 million metric tons

2019 (only subsonic possible)

2035 (subsonic)

2035 (subsonic and supersonic)

Sources: International Council on Clean Transportation, International Civil Aviation Organization, International Energy Agency, US Energy Information Administration, International Air Transport Association. Note: Projected CO 2 emissions for subsonic aircraft in 2035 calculated by multipling projected fuel use by 21.10 lb CO 2 emitted per gallon of jet fuel burned.

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• PLANET POSSIBLE

Greener air travel will depend on these emerging technologies

Electric engines, alternative fuels, and better navigation could reduce emissions—and mitigate the impacts of a global return to the skies.

The sky over Cologne, Germany, is crisscrossed by condensation trails from airplanes. Because the pollutants in these so-called “contrails” contribute to climate change, researchers are studying ways to eliminate them—one of several ongoing efforts to make flying more sustainable.

Here’s a word you may have overlooked in 2020: flygskam, a Swedish term for the feeling of being ashamed to fly. In a year that saw a 66 percent decrease in flights, compared to 2019, you might think that flygskam has flown the coop.

But with a recent uptick in air traffic—and the anticipation of travel’s rebound thanks to COVID-19 vaccines —flygskam is taking flight again. The term originated in 2017 as part of a campaign to change how we fly, from the frequency of our flights to the technology of our aircraft. The goal: to mitigate the carbon dioxide emissions that experts think may triple by 2050 .

Aviation accounts for a relatively small portion of global emissions—2.5 percent. While bigger culprits, such as electricity and agriculture, account for greater emissions, they also benefit billions of people. Airline emissions, in contrast, come mostly from rich travelers in the richest countries: business class passengers produce six times as much carbon as those in economy class, and one percent of the most frequent fliers are responsible for half of all aviation’s carbon emissions.

Will the pandemic -caused travel slowdown be enough to shake up aviation and produce lasting benefits for the environment? In 2020, the drop in air traffic likely reduced carbon emissions by several hundred million tons . Some are calling to make those reductions permanent by eliminating contrails, using new fuels, improving navigation, and more. With climate change reaching a point of no return as early as 2035 , action will need to happen quickly.

( Wondering what you can do? Here are 12 ways to travel sustainably in the new year .)

Of course, flying less would have an even bigger impact, and there are calls for travelers to fly only once a year , give up flying for a year , and attend conferences virtually . Still, air travel is here to stay, so the cleaner the better. Here are some of the ways flying could clean up its act in the years to come.

Curtailing the contrails

Aviation emits more than carbon dioxide; it also produces water vapor, aerosols, and nitrogen oxides. These pollutants absorb more incoming energy than what is radiated back to space, causing Earth’s atmosphere to warm. This means aviation’s impact on warming might be an even bigger share than its carbon footprint.

The turbine engines of commercial aircraft, like this one at a maintenance facility in Singapore, rely on kerosene-based propellants. Companies are experimenting with biofuels and synthetic fuels that can reduce carbon dioxide emmissions.

An Airbus A300-600R makes its final approach before landing. The company plans to have a hydrogen-fueled plane in service by 2035.

The worst of the non-carbon impacts are from contrails, short for condensation trails: the line-shaped clouds that form from a plane’s engine exhaust. A small number of flights are responsible for most contrails. This is because contrails form only in narrow atmospheric bands where the weather is cold and humid enough.

Avoiding those zones could make a big difference in limiting aviation’s non-carbon pollution. One research paper modeling Japan’s airspace found that modifying a small number of flight routes to skip these areas could reduce contrails’ effects on the climate by 59 percent. The change would be as little as 2,000 feet above or below these regions. While flying a plane higher or lower can reduce its efficiency and require more jet fuel, the paper found that limiting contrails would still offset any additional carbon emissions.

“There is a growing realization that the impact of contrails is a really significant component of aviation’s climate impact,” says Marc Stettler, one of the paper’s authors and a lecturer on transport and the environment at Imperial College London .

The spots where contrails can form change from day to day, so airlines need accurate, multi-day weather forecasts to avoid them. In the future, pilots could report contrails, much like they now do with turbulence, so other planes could adjust their flight paths.

The EU’s aviation authority, EUROCONTROL, starting preparing last year to conduct trials on a contrail avoidance project . Stettler and his colleagues plan to continue research on how to go about implementing changes that could reduce contrails.

“This is the faster way that aviation can reduce its climate impact,” he says.

Related: Stunning views from an airplane window

Harnessing alternative fuels

Commercial airplanes rely on kerosene-based propellant, but companies are experimenting with turning biomasses, such as vegetable oil and even used diapers , into jet fuels. Some research suggests these biofuels could cut carbon pollution from airplanes by upwards of 60 percent . But all biofuels are not created equal.

Those that could be processed into food are unsustainable because of the planet’s growing population, which needs crops for calories. Used cooking oil and pulp leftover from agriculture or logging are expensive and not produced at a scale large enough to make a meaningful difference. But this doesn’t mean that other sustainable aviation fuels won’t be developed.

( How clean is the air on planes? Cleaner than you may think .)

“You hear that aviation is a hard sector to decarbonize,” says Andrew Murphy, the aviation director at Transport and Environment , a European nongovernmental organization. “That is only half the story. The other half is we haven’t tried.”

More-promising areas include e-fuels, or “synthetic fuels,” which don’t require engines to be reengineered. To make e-fuels, electricity—hopefully renewable—is used to split water into hydrogen and oxygen. The hydrogen is then combined with carbon dioxide to make jet fuel. KLM recently conducted its first flight powered by synthetic fuel.

Another effort entails pulling carbon out of the atmosphere and using it as an ingredient in fuel. Although this technology is still in early stages, that doesn’t mean it has to be far off.

“The pandemic has shown us new technology can be sped up if we want it to,” Murphy says.

Going electric or hybrid

Cars aren’t the only conveyance undergoing electric innovation: one count found a hundred electric-powered aircraft projects in the works.

The first electric flights will be in small planes with a range limited to a few hundred miles. Norway , a country with numerous islands and mountainous terrain calling for puddle jumpers, has promised that all of its short-haul flights will be on electric aircraft by 2040 . Underserved areas could one day get new routes flown exclusively by electric planes.

“A huge fleet of these could radically change local transportation systems,” says Ron Steenblik, former director of the International Institute for Sustainable Development ’s Global Subsidies Initiative.

An airplane descends as the sun rises on Mexico City. Artificial intelligence is being used in efforts to improve flight navigation and lessen delays that cause planes to sit on the tarmac or circle the airport.

Going farther or flying bigger planes with electrification isn’t on the near-term horizon. But some companies are exploring a hybrid of electricity and hydrogen, which could extend ranges. Boeing and others are also looking at hydrogen as a means of propulsion even without electrification. Airbus recently revealed three different hydrogen planes with plans to have one or something like it in service by 2035.

“We don’t want to just make it technically feasible,” says Glenn Llewellyn, vice president of Airbus’s Zero-Emission Aircraft project. “We want to make it economically viable.”

The Hindenburg disaster in 1937 ended the first hydrogen era. The aviation industry tried and dropped a hydrogen effort again in 2010 after finding it too expensive. But Llewellyn points out that hydrogen has been improved by other industries, such as automobile and space, proving its safety, innovating on its uses, and bringing down its costs.

“The ecosystem is evolving in a much different way than 10 years ago,” Llewellyn says. “We have a better starting point.”

Giving navigation an upgrade

Airlines have used computers to help optimize routing and planning for decades, but they’re now putting artificial intelligence (AI) to work in finding new ways to reduce jet fuel needs.

Air France, Norwegian, and Malaysia Airlines are already using technology called Sky Breathe that relies on big data and AI to analyze billions of records from flights in an effort to find ways to save fuel. The company behind Sky Breathe says it has saved its customers more than $150 million in 2019 and reduced CO2 emissions by 590,000 tons.

The U.S. Federal Aviation Administration (FAA) is midway through a multiyear upgrade called NextGen , which will be a series of interconnected systems to improve how air traffic control sees, navigates, and communicates. The FAA says the technology will make it possible to schedule tighter landings and takeoffs and decrease delays that leave planes sitting on the tarmac or circling the airport.

“AI is really good at looking at patterns,” says Ashish Kapoor, an AI researcher at Microsoft who works on aviation projects. “We have years of experience of flying planes, so we have a lot of data out there.”

There will be more data as planes get kitted out in sensors, which will produce additional insights into improvements. All that data means that the next stage of aviation could look different. Algorithms could develop new plane designs and come up with flight plans, taking into account speed, comfort, and emissions.

“We don’t have to evolve like aviation has done the last hundred years,” Kapoor says.

But for this to happen, more than technology has to evolve; countries will need to change legislation, and airlines will need to fund expensive research. It will take incentives to encourage the aviation industry to become sustainable. Janice Lao-Noche, an environmental scientist and development economist, says it’s going to take a lot of flygskam and maybe the pain of climate change disrupting more flights for all the innovations to take off.

“I don’t think it’s futile,” Lao-Noche says. “[But] this is going to be, no pun intended, a bumpy ride for the aviation industry.”

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• SUSTAINABLE TOURISM

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• Open access
• Published: 22 June 2021

Evaluating the climate impact of aviation emission scenarios towards the Paris agreement including COVID-19 effects

• Volker Grewe   ORCID: orcid.org/0000-0002-8012-6783 1 , 2 , 3 ,
• Arvind Gangoli Rao   ORCID: orcid.org/0000-0002-9558-8171 2 , 3 ,
• Tomas Grönstedt 3 , 4 ,
• Carlos Xisto   ORCID: orcid.org/0000-0002-7106-391X 3 , 4 ,
• Florian Linke   ORCID: orcid.org/0000-0003-1403-3471 3 , 5 ,
• Joris Melkert 2 , 3 ,
• Jan Middel 3 , 6 ,
• Barbara Ohlenforst   ORCID: orcid.org/0000-0002-5793-6059 3 , 6 ,
• Simon Blakey   ORCID: orcid.org/0000-0001-6478-7170 3 , 7 , 8 ,
• Simon Christie   ORCID: orcid.org/0000-0003-2631-5425 3 , 9 ,
• Sigrun Matthes   ORCID: orcid.org/0000-0002-5114-2418 1 , 3 &
• Katrin Dahlmann 1 , 3  

Nature Communications volume  12 , Article number:  3841 ( 2021 ) Cite this article

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• Climate change
• Climate-change mitigation
• Environmental impact
• Projection and prediction

Aviation is an important contributor to the global economy, satisfying society’s mobility needs. It contributes to climate change through CO 2 and non-CO 2 effects, including contrail-cirrus and ozone formation. There is currently significant interest in policies, regulations and research aiming to reduce aviation’s climate impact. Here we model the effect of these measures on global warming and perform a bottom-up analysis of potential technical improvements, challenging the assumptions of the targets for the sector with a number of scenarios up to 2100. We show that although the emissions targets for aviation are in line with the overall goals of the Paris Agreement, there is a high likelihood that the climate impact of aviation will not meet these goals. Our assessment includes feasible technological advancements and the availability of sustainable aviation fuels. This conclusion is robust for several COVID-19 recovery scenarios, including changes in travel behaviour.

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Definitions and implications of climate-neutral aviation

Cost and emissions pathways towards net-zero climate impacts in aviation

Pathways to net-zero emissions from aviation

Introduction.

Fuel efficiency of jet aircraft has been increasing right from the dawn of jet aviation in the late ’50 s and early ’60 s. This improvement cannot be attributed to one single source but has been achieved by a combination of factors such as improvements of the airframe aerodynamics, weight reductions due to better engineering, materials and manufacturing techniques, larger engines with a lower specific thrust, higher overall pressure ratios and component efficiencies, lighter structures and lighter on-board systems. Kharina and Rutherford 1 report an average reduction in fuel consumption per passenger-km at the global fleet level of 1.3% per year over the years 1960–2014. Without any further specific measures this reduction is expected to continue at a similar rate until 2037 2 in a business as usual scenario.

Air transport as a sector has been growing rapidly in most regions of the world. The total number of passengers transported annually passed 4 billion in 2017. The number of flights in all regions of the world has increased (Supplementary Fig. 1 ) and aircraft have on average greater seating capacity and are operated with a higher load factor (Supplementary Fig. 2 ). It is expected that air transport will continue to grow in the coming decades. Airbus 3 predicts in its Global Market Forecast continued annual growth of 4.4% in revenue passenger kilometre (RPK) for the next two decades. Boeing 4 expects in its Commercial Market Outlook an annual growth of 4.6%. The effects of the COVID-19 pandemic are expected to only have a temporary effect on this growth.

Without any measure the climate impact of aviation will continue to grow. Several measures, both political and technical, are in place or will be introduced in the near future. Via a number of scenarios, we analyse their effect on global warming and assess the effectiveness of these measures. Since many of these measures are set top-down we also want to assess the technical feasibility. Therefore, we have performed a bottom-up expert assessment on the feasibility of technical advances and their effect on climate change. We confront the two approaches with each other.

The profitability for the airlines is small. Their average net profit per passenger is <10 USD (Supplementary Fig. 3 ). Competition amongst airlines is fierce and therefore sensitive to airline costs differences. Fuel costs play an important role, which is of particular concern for the uptake of sustainable alternative fuels (SAF) that currently have a significantly higher cost than conventional fossil fuels. The COVID-19 pandemic has led to a large decrease in the number of flights and passenger load factors in 2020. In May 2020, the International Civil Aviation Organisation (ICAO) estimated a decrease of global total available seat kilometres of 94% in April 2020 compared to the 2019 baseline. However, they expect a recovery leading to an annual decrease in available seat kilometres of 45% to 63% for 2020 5 , but assume growth will resume beyond 2020.

Approximately 5% of the current anthropogenic climate change is attributed to global aviation 6 , 7 and this number is expected to increase since aviation passenger transport is projected to grow by ~4% per year whilst other sectors continue to decarbonise. Aviation emits carbon dioxide (CO 2 ), water vapour (H 2 O), nitrogen oxides (NO x ), sulphate aerosols, compounds from incomplete combustion (unburnt hydrocarbons, UHC) and particulates (soot). The emitted species are transported in the atmosphere and alter a wide range of atmospheric processes including the formation of contrail-cirrus and ozone and the depletion of methane 7 , 8 , 9 .

The formation of persistent contrails-cirrus depends on aircraft and fuel parameters as well as atmospheric conditions, as the propensity of contrail formation is higher in the cold and saturated atmosphere 10 , 11 , 12 . Contrail-cirrus influence the incoming solar radiation and the outgoing infrared radiation emitted by the Earth and its atmosphere. The net change, the radiative forcing (RF), is on average positive and hence contrail-cirrus act to warm the climate 13 . The emitted nitrogen oxides (NO x ) react with hydroxyl radicals (HO x ), which eventually form ozone and contribute to the depletion of methane in the atmosphere. Therefore, emissions of nitrogen oxides increase the ozone concentration and decrease the methane concentration (which itself leads to a reduction in ozone production and is called primary mode ozone, PMO). Ozone and methane are greenhouse gases and changes in their concentrations cause changes in the RF, which are in total positive, i.e. leading to warming 7 , 14 , 15 . The net direct impact of aerosol emissions on RF (soot: warming and sulphate: cooling) is small 7 and are not further regarded in this study, whereas the impact of soot emissions on contrail-cirrus properties are important 16 and considered in our calculations (see ‘Methods’). An open question, which is currently under investigation is whether aerosol emissions significantly alter or even induce natural clouds, both low-level and cirrus clouds 17 .

The Advisory Council for Aviation Research and Innovation in Europe (ACARE) has set targets for the reduction of emissions in its Flightpath 2050 document 18 . Among these targets is a reduction of 75% of CO 2 and 90% of NO x emission per passenger-km by 2050. The datum for these reductions is a typical new aircraft in the year 2000. These targets are set for the research, with intended outcomes to be realised at a technological readiness level (TRL , The European definition of TRLs range from 1 to 9, i.e. from ‘basic principles observed’ to ‘actual system proven in operational environment’) of 6.

The ICAO of the United Nations has agreed on a global market-based measure scheme to abate the growth of CO 2 emissions from international aviation. This scheme is the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). According to this scheme, the post-2020 growth in the sector must be offset such that the net carbon emissions do no longer grow. They must either be reduced via more efficient aircraft and/or the use of SAF or must be compensated via offsets. CORSIA starts as a voluntary pilot scheme in 2021 and becomes mandatory, with some exceptions, in 2027 for all member states 19 . Aviation is a growing sector that has committed to reduce net CO 2 emissions and thus contributes to the international goals of limiting climate warming ‘to well below 2.0° C above preindustrial levels and pursuing efforts to limit the temperature increase to 1.5 °C above preindustrial levels’, as stated in the Paris Agreement 20 . The Paris Agreement does not set emission targets for specific sectors. Furthermore, international aviation and shipping are not included in the national contributions that countries have to make to comply with the agreement. However, we assume that the international aviation community will contribute to the goal of the Paris Agreement. We will investigate the effect of measures and policies on global warming and also assess their feasibility. Thereby we will not distinguish between domestic and international aviation but treat the sector as a whole. There are two bridges to cross between the emission goals set by ACARE and ICAO and the climate targets set by the Paris Agreement: First, how do the emission goals translate into near-surface temperature changes, i.e. climate change. Second, how large are the non-CO 2 effects?

Here we close these gaps and show that the emissions goals set by Flightpath 2050 very likely will stabilise aviation’s climate impact, though the sector’s contribution to global warming remains considerable. Contrarily, we find that ICAO’s offsetting scheme, CORSIA, will surpass the climate target set to support the 1.5 °C goal between 2025 and 2064 with a 90% likelihood. In both cases non-CO 2 effects will have a considerable contribution to aviation’s climate impact, however, they are currently not included in ICAO’s goal of climate neutral growth and only partly addressed in Flightpath 2050. We assess the feasibility of achieving the Flightpath 2050 goals by technological improvements and the availability of sustainable alternative fuels as an ECATS (Environmentally Compatible Air Transportation System) expert group and reveal the risk of a large discrepancy, leading to an increasing aviation induced global warming effect rather than stabilisation.

Results and discussion

Top-down scenarios for future aviation.

Figure  1a presents the global growth of revenue passenger kilometres, showing an exponential increase between 5.2 and 6% per year (dotted lines). From this basis, we developed eight top-down scenarios, which consider a further increase in aviation, though with a decreasing rate of growth (down to 1.2%/year). These rates are based on simulations of the aviation sector, relying on the Randers scenario 21 , which is independent from aircraft manufactures. This scenario was employed within the WeCare project 22 and considers worldwide saturation effects of economic growth. This Randers scenario leads to a growth rate of 1.2%/year in 2050 which we extrapolate to 0.8%/year in 2100 (see also Supplementary Material). Our industry-independent scenario shows lower estimates of the transportation volume for the coming two decades compared to the Airbus and Boeing forecasts (see above), though still slightly higher than other estimates for 2050 23 , 24 . Advances in airline operating efficiency, including changing the type of aircraft, the number of seats and load factor lead to a reduced increase of flown kilometres (Fig.  1b ; green line) compared to the transport volume measured in RPKs (violet line). More fuel-efficient technologies even lead to a smaller increase in fuel use compared to flown distances (blue and orange lines). Taking the targets of Flightpath 2050 into account, a more aggressive reduction in emissions can be achieved up to 2050. In the scenario FP2050, we consider a development of these technologies until 2050 followed by an introduction into the market. In the scenario FP2050-cont we apply a continuous introduction of these innovative technologies into the market (Fig.  1b , early and continuous/late introduction light/dark brown, respectively). Using these assumptions, the modelled results show that after 2050 the increase in RPK is balanced by technology enhancements leading to almost constant fuel consumption until 2100.

They include the future use of current technology, i.e. without technology improvements (CurTec), with a business-as-usual future technological improvement (BAU), the offsetting scheme of the international civil aviation organisation (CORSIA), and 2 Flightpath 2050 scenarios which differ in the speed of technology improvements (FP2050 and FP2050-cont). a Revenue passenger kilometres as provided by ICAO; dotted lines provide exponential growth rates. b Future changes relative to their respective values in the year 2000 for revenue passenger kilometres (violet), flown distances (green), the fuel consumption of the scenarios BAU and CORSIA (blue), and the FP2050 scenarios (brown). c Future CO 2 emissions for the scenarios CurTec (red), BAU (blue), CORSIA (light blue), FP2050 with late technology advancements (dark brown) and continuous technology advancements (brown). Note that for CORSIA the effective CO 2 emission is considered, including reductions due to the use of sustainable alternative fuels (SAF) and capping net emissions. d as bottom-left, but for NO x emissions; note that the NO x emissions for BAU and CORSIA are identical. The order in the legend is the same as the lines appear in the graph.

We take into account five different scenarios (Table  1 ): (1) Current Technology (CurTec), which describes the emission pathways with current (2012) technology, (2) Business-as-usual (BAU), which, in addition, takes into account some of the future improvements in technology, (3) CORSIA, which is identical to BAU, but yearly CO 2 emissions are reduced by offsetting CO 2 emissions beyond 2020 values, (4) and (5) Flightpath 2050 (FP2050 and FP2050-cont), which utilise the targets of FP2050 (Fig.  1c, d ). Note that for the CORSIA scenario, we assume an optimistic future availability and a price premium of SAF based on an analysis of feedstocks and the evolution of SAF production. As a result, approximately half (53%) of the CO 2 reduction that is required to achieve CORSIA’s CO 2 -neutral growth stems from the use of SAF and the other part results from carbon caps. This leads to a larger reduction in climate impact compared to a scenario where the total amount of CO 2 is capped. The explanation is that SAF do not only reduce the climate impact via CO 2 but also the reduction in contrail-cirrus climate impacts since a change in their chemical composition changes the contrail-cirrus properties (see ‘Methods’).

Aviation climate impact

We use these five scenarios to calculate their climate impact with the non-linear climate-chemistry response model AirClim 25 , 26 in terms of near-surface temperature change by taking into account effects from CO 2 as well as NO x and H 2 O emissions and contrail-cirrus (Fig.  2 ). The three scenarios CurTec (red line), BAU (dark blue line), and CORSIA (light blue line) show an increase in temperature until the end of the simulation (2100), though the rate of increase slows down. For CurTec, since the technology is frozen in this scenario, the rate of increase arises from the assumed development of the transport volume (Fig.  1 ). The increased efficiency in scenario BAU in comparison to the scenario CurTec clearly shows a substantial temperature reduction of roughly 25% in 2100. The temperature reduction is even larger for CORSIA (35–40%), due to a reduction in the effective CO 2 emissions from the CORSIA scheme and changes in contrail-cirrus properties from the extensive use of SAF. Terrenoire et al. 27 calculated a temperature increase in 2050 for a CORSIA scenario of 32 mK, which is consistent with our calculated value of 30.4 mK. The two implementations of the Flightpath 2050 scenarios (FP2050 and FP2050-cont) show a clear stabilisation of their climate impact, though with an overshoot around 2050. Allowing 5% of the anthropogenic temperature increase to be contributed by the aviation sector, as motivated by the current estimate of aviation to global warming, both scenarios show compliance with a 2 °C target and the scenario FP2050-cont even with the 1.5 °C target. The inertia of the climate system delays the impact of both FP2050 scenarios, which overshoot these targets around the year 2050. However, after 2050, the FP2050 measures are sufficient to cause significant temperature decreases beyond these targets from this point on.

The horizontal lines indicate 5% of a 2 °C and 1.5 °C climate target. The scenarios describe a future use of current technology, i.e. without technology improvements (CurTec, red), a business-as-usual future technological improvement (BAU, blue), the offsetting scheme of the international civil aviation organisation (CORSIA, light blue), and 2 Flightpath 2050 scenarios which differ in the speed of technology improvements (FP2050 and FP2050-cont, brown and orange, respectively).

Temperature change is a complex response to the individual measures through the various climate agents. The reductions of the CO 2 emissions (Fig.  1 ) for all scenarios compared to the CurTec scenario lead to a significant reduction of aviation’s absolute contribution to climate change (Fig.  2 ). However, the relative contribution to climate change, i.e. the share of CO 2 to the aviation’s climate impact, increases from 25% in 2005 to between 33% and 56% in 2100. The reason is that the reduction in NO x emissions reduces the temperature increase via ozone faster than the reductions in CO 2 emissions. The short lifetime of both NO x and ozone in the atmosphere compared to CO 2 enables this faster response. On the other hand, the contrail-cirrus climate impact is largely driven by the distances flown. Here two factors play a role, the increase in the efficiency of the transportation system and the use of sustainable alternative fuels. These two effects lead to a reduction in the contrail-cirrus climate impact by roughly 20% in the scenarios BAU and CORSIA compared to CurTec (Fig.  3 ). The relative contribution of contrail-cirrus to the climate impact (Table  2 ) shows a reduction from 33% in 2005 to around 20% and 24% in 2100 for BAU and CORSIA scenarios, respectively, and is only slightly reduced for the FP2050 scenarios (27% and 30%). Recently, the non-CO 2 effects of aviation were revised concerning NO x emissions 15 and contrail-cirrus 13 . While Grewe et al. 15 stressed methodological improvements, like how to correctly attribute ozone concentrations to aviation NO x emissions, Bock and Burkhardt 13 focussed on improved contrail-cirrus microphysics. Our results include most aspects of these new developments and hence show, e.g. a larger ozone-RF as well as NO x -RF compared to earlier studies, such as Lee et al. 28 (Fig.  3 , left bars). The current results are in accordance with those new findings.

The individual bars are grouped into four categories. (1) The two bars on the left describe the radiative forcing of aviation in the year 2005 (RF 2005). Results from Lee et al. (2009) are expanded by contrail-cirrus estimates based on Bock and Burkhardt (2019), denoted by L09 + BB19, respectively; (2) temperature change in the year 2005 (dT 2005); (3) temperature change in the year 2050 for the 5 scenarios (dT 2050); (4) as (3), but for the year 2100 (dT 2100). For 2100, i.e. the right-hand columns, the scenarios are presented in the same order as for 2050. The order in the legend is the same as the colours appear in the individual boxes. The scenarios describe a future use of current technology, i.e. without technology improvements (CurTec), a business-as-usual future technological improvement (BAU), the offsetting scheme of the international civil aviation organisation (CORSIA), and 2 Flightpath 2050 scenarios which differ in the speed of technology improvements (FP2050 and FP2050-cont).

Hence to summarise, the increase in transport volume leads to an increase in the overall climate impact from aviation, which also increases the relative importance of CO 2 (25% in 2005 Base to 39% in 2100 CurTec, Table  2 ), even if aviation net CO 2 emissions are regulated and capped to 2020 values. The increase in fuel efficiency of aviation technologies at a current rate decreases the overall climate impact, especially for CO 2 and NO x . By this, it mainly reduces the relative contribution of NO x (41–16%). The introduction of the CORSIA scheme further reduces the climate impact of CO 2 emissions and that increases the relative importance of contrail-cirrus and NO x . The technological measures from FP2050 have a similar reduction efficiency for CO 2 as CORSIA, however, the strong measures for NO x largely reduce the overall climate impact so that the remaining climate impact from aviation is due to CO 2 (50–60%) and contrail-cirrus (around 30%).

Contrasting aviation climate impact with 1.5 °C and 2 °C climate targets

The climate impact of aviation emissions has a considerable uncertainty range, especially, for the non-CO 2 effects 22 , 28 , which influences not only the absolute change of near-surface temperatures but also the importance of the individual climate agents. In this work, we take into account uncertainties in the atmospheric lifetime of aviation-related species, uncertainties in the RF of individual species and the climate sensitivity parameter, the last of which relates the RF to temperature changes. These parameters are varied in a Monte–Carlo analysis with 10,000 simulations to obtain a range of possible atmospheric responses. The results of the Monte–Carlo analysis provide a basis for estimating a range when the temperature thresholds, 5% of 1.5 °C and 5% of 2 °C, are surpassed. For example, Fig.  4a shows the first 20 simulations of the CORSIA scenario. Figure  4b shows the probability density function (blue) and cumulative probability density function (green) of these times of surpassing the 5% of 1.5 °C for the CORSIA scenario. The mid 90% range (between the 5% and 95% percentile) indicates that this threshold is surpassed between 2025 and 2064 in the CORSIA scenario. The 5% of 2 °C is surpassed roughly 10 years later (Fig.  4c ). Both, the CurTec and BAU scenario, show that both thresholds are surpassed very likely well before 2050 (Fig.  4c ).

a Potential pathways (first 20 realisations of the Monte–Carlo simulation) for the CORSIA Scenario (grey). 5% of the 1.5 °C ( = 75 mK) is indicated as a black line. Crossings of the brown line with the grey line indicate the year when the threshold is surpassed. b Probability density function (PDF, blue) and cumulative probability density function (CPDF, green) for the year in which the climate target of 5% of 1.5 °C is surpassed (and stays above). The horizontal bar indicates the 95%, 50% and 5% percentiles. c 95%, 50% and 5% percentiles of the year in which the climate target is surpassed for 5% of 2 °C (thin top lines with crosses) and 5% of 1.5 °C (thick bottom lines). For both FP2050 scenarios, the 5% of 2 °C target is not surpassed in >95% of the cases, hence there is no thin line, and for FP2050 scenario with continuous improvements (FP2050-cont) the 50% percentile is beyond 2100. The scenarios describe a future use of current technology, i.e. without technology improvements (CurTec), a business-as-usual future technological improvement (BAU), the offsetting scheme of the international civil aviation organisation (CORSIA), and 2 Flightpath 2050 scenarios which differ in the speed of technology improvements (FP2050 and FP2050-cont) and bottom-up estimates based on a group of experts from ECATS (Environmentally Compatible Air Transportation System).

ECATS technology scenarios and their climate impact

The emission reductions formulated in the Flightpath 2050 are aspirational goals, which the aviation community is aiming to achieve. Here we now contrast this with technologies which are currently discussed in the research, such as boundary layer ingestion, distributed propulsion, laminar flow control, lightweight structures, advanced geared turbofan engines, etc., and assess their potential to reduce fuel use and NO x emissions (Table  3 and Supplementary Material for more details). The majority of technology enhancements for a 2050 aircraft should, at least as an idea, be available today since the time from the development of basic research ideas (TRL 1) to having this aircraft operational in service (TRL 9) takes decades. We take into account developments for different aircraft segments, such as single-aisle and twin-aisle aircraft for entry into service between 2035 and 2050. General aviation, regional aircraft and business jet have been left out from this study, as their current contribution to total aviation CO 2 emission is around 5–6%, only. We take into account a large range of technologies and engine airframe integrations (see Supplementary Figs. 7, 12–16 ) and find a 18–22% improvement in fuel efficiency, which is similar to the analysis presented by Cumpsty et al. 2 , which indicates an 18% reduction. For the far future (2050), we consider one variant for a single-aisle aircraft, while three variants are considered for a future long-range twin-aisle aircraft. These include (1) a conventional tube-and-wing wide-body aircraft (TW), (2) the so-called Flying-V (FV) or multi-fuel blended wing body (MF-BWB). Both have similar aerodynamic characteristics and were developed by TU Delft 29 , 30 , 31 , 32 and (3) NASA’s N3-X (N3) blended wing body 33 , 34 . We find that the fuel consumption of a 2035 aircraft might be reduced between 18% and 22% compared to new 2015 aircraft and between 34% and 44% in 2050. Note that though far future technologies, i.e. in 2075 or later, are in principle of interest they do not significantly impact our results, since their diffusion into the fleet delays their impact and more importantly, the impact on global temperatures will mainly occur beyond 2100 due to the inertia of the atmosphere-ocean system in the order of decades. These findings result in 9 ECATS emission scenarios with 3 variants (TW, FV, N3) including a pessimistic base and an optimistic implementation, which differ by ±10%. The scenarios are developed consistently with the top-down scenarios following the same transport volume development and SAF usage as in the scenario CORSIA. Figure  5a presents the fuel use and NO x emissions relative to the year 2000, resulting in a roughly fivefold increase in fuel consumption by 2100 and a fourfold increase in NO x emission. The new technologies introduced from 2035 onwards lead to a reduction in fuel use and NO x emission around 2050, which is then offset by the further increase in transport volume, resulting in a slight increase in fuel use and NO x emission until 2100. This analysis shows that an emission pathway better than BAU might be feasible, but that the goals set by Flightpath 2050 are unlikely to be achieved. The fuel use and NO x emission from the FP2050 scenario (Fig.  1 ) are drastically lower than the range of our ECATS scenarios (Fig.  5 ).

a as in Fig.  1 , changes in fuel use (red) and NO x emissions (blue) taking into account a bottom-up analysis of aviation technologies; three far future technology pathways are taken into account, with a ± 10% uncertainty range, each leading to a scenario range; b Transport volume for the scenario taking into account a reduction of flight due to COVID-19 with three assumptions: a short recovery of 3 years (red); a longer recovery of 15 years (brown) and in addition to a long recovery a behavioural change after COVID-19 (yellow). c Resulting temperature changes as in Fig.  2 for the range of ECATS scenarios (green) and the BAU scenario for comparison (blue). d Resulting temperature changes from the 3 COVID-19 scenarios (red, brown, and yellow) in comparison to the BAU scenario (blue). The scenario BAU describes a business-as-usual future technological improvement and ECATS bottom-up estimates based on a group of experts from ECATS (Environmentally Compatible Air Transportation System).

The climate impact of the ECATS aviation scenario (Fig.  5c ) shows clearly a reduction compared to the BAU scenario. However, the stabilisation of the temperature, as it was found for the Flightpath 2050 scenarios, is not achieved. The ECATS scenarios fall in between the BAU and FP2050 scenarios. The absolute change in temperature and the contribution from individual climate drivers (Table  2 ) contribute to climate warming in 2100 from CO 2 of 33–37% and the effects from non-CO 2 emissions roughly equally shared between contrail-cirrus and NO x emissions.

Sensitivities to growth, global targets, sustainable fuels and technologies

The future evolution of the aviation system and the resulting impact on climate relies on too many variables to be predicted with one outcome. To tackle this problem, we present a range of scenarios. Those are based on either an analysis of climate impacts based on set emission targets, the five scenarios mentioned in Table  1 , which we call top-down scenarios, or an analysis of the climate impact of technological changes that can be expected in future aircraft, which we call the bottom-up scenarios (see ‘Method’). Both approaches define possible future pathways. Even though this approach includes a large range of uncertainties, we feel that such analysis should be an important part of the debate around the impact of aviation and the potential for change within the sector. A major uncertainty is the future demand for air travel. Here we present a scenario, which lies between the estimates from Boeing and Airbus (see above) other estimates from academia 23 , 24 which levels off in the future. In this sense, we present a more conservative estimate of the future climate impact of aviation as compared to industry forecasts. A variation of the future growth rates by ±50% on top of the general declining growth rate leads to a change of fuel usage in the scenario BAU of roughly ±20% in 2100 and a shift in the median surpass year of 3 years (Table  4 ). Demand-suppressing effects from the use of more expensive SAF might end up at about 10–15% reduction of demand by 2050 for an elasticity of −1 35 and a SAF price, at best, two times that of conventional kerosene 36 . Hence, our ‘−50% growth rate’ sensitivity simulation can be taken as an indicator for the impacts of such demand-suppressing effects, implying that the median year at which the temperature rise of 5% of 1.5 °C is surpassed will be delayed by a few years only. Most other scenarios lead to a similar shift in the median surpass year. A change in future efficiency improvements has in principle similar effects. The overall setting of the climate target and a shift from 5% to either 3.5% or 6.5% leads to a shift of the median surpass year in the order of one to two decades (Table  4 ). Sustainable aviation fuels are an important means in reducing the climate impact of aviation. However, according to CORSIA, whether a cap in net CO 2 is achieved by offsetting or the use of SAF has only a limited impact on the temperature evolution. And hence a reduction of the SAF availability by 50% leads to negligible changes in the distribution of the surpass years.

COVID-19 effects on aviation climate impact

The recent COVID-19 pandemic might question the discussed future aviation pathways we analysed so far. To better understand the possible implications of this pandemic on the climate impact of aviation, we altered the BAU scenario in a parametric way to assess three different pathways for the international recovery from the lock-down of nation states and the associated dramatic reduction in air travel, based on reported transport volumes and scenario projections 5 . We take into account a fast recovery of 3 years, a slow recovery of 15 years (C19-03, C19-15) and a change in habits due to experiences during the lock-down, for example, a shift towards web conferences instead of face-to-face meetings. Figure  5b shows a drop in RPK due to COVID-19 and the three recovery pathways. The respective, resultant temperature change (Fig.  5d ), however, is only significant if a sustained reduction in RPKs follows the crisis (yellow curve). Otherwise, the changes in 2020 due to COVID-19, as dramatic as they are for individuals and the global economy, only have a minor effect on the overall climate impact of aviation as long as a recovery follows. From the experience of other crises (e.g. SARS, 9-11, etc. see Fig.  1 ) we might expect a fast recovery. However, the consideration of which COVID-19 scenario is more likely is outside the scope of this study.

Top-down-scenario building

In the top-down scenario building, we combine top-level assumptions on the evolution of aviation (transport volume, technologies, SAF availability) with a detailed description of the air transport system for specific years. Details are given in the Supplementary Material as textual description and EXCEL sheet. Five scenarios are assessed, which all have some common characteristics (Table  1 ). They have identical evolution in transport volume, defined by the revenue passenger kilometres, which resemble ICAO data for the past (1971–2017) and are extrapolated to future with the assumption of a slow decrease in traffic growth rates in future. The observed increase rate in transport volume of roughly 6% per year in the decade 2008–2017 are reduced by to roughly 1% per year in 2050 following the results from the WeCare analysis and the Randers scenario. We employed the Randers scenario named 2052 that includes the temporal development of socio-economic factors, such as population and Gross-Domestic Product, for different world regions and is complemented by reasonable narratives and scientific evaluations. Within the WeCare project, it was combined with an air passenger demand model that calculates the demand between settlements. The resulting air traffic scenario shows lower estimates of the transportation volume for the coming two decades compared to the Airbus and Boeing forecasts. The resulting air traffic scenario is not based on an extrapolation of historical trends and manufacturer expectations but considers realistic assumptions for the socio-economic growth and an associated expected saturation around 2040. Details on the forecasting methodology developed and applied in WeCare can be found in Terekhov 37 and Ghosh 38 . Future fuel efficiency improvements are based on the ICAO’s environmental report 39 , with 1%/year in 2018 decreasing to 0.25% in 2100. These two assumptions lead to a fuel consumption of 823 Tg in 2050, which agrees well with the mean of the ICAO scenarios 39 . The geographical distribution follows the emission inventories developed within the WeCare project 22 . Two time horizons are taken, one for the recent past ( = 2012) and one representative for the future (2050), describing the geographical and vertical distribution of the emissions. All scenarios are identical between 1940 and 2018, and deviate afterwards, according to scenario assumptions, derived from the basic storylines. Thereby, we obtain 5 scenarios CurTec, BAU, CORSIA, FP2050, FP2050-cont (see main text and Table  1 ). The carbon-neutral growth from 2020 onwards in the CORSIA scenario is achieved by using a combination of sustainable aviation fuels (SAF) and emission offsets. Based on the EU-Renewable Energy Directive (RED-II), we assume an effective 65% net CO 2 reduction in SAF production and use compared to conventional kerosene in the year 2020. We assume a mix of different feedstocks, such as agricultural residues, algae, dedicated energy crops and also e-fuels (power-to-liquid), which enables an improvement of the overall CO 2 reduction potential to 80% in 2100. An analysis of the current growth rates and forecasts of the availability of SAF are used to optimistically estimate future availability of SAF and to allow a conservative estimate of the climate impact of the CORSIA scenario. Note that we have not explicitly considered any closed loop demand-supressing effects of increased costs 35 , such as SAF costs, since EUROCONTROL has indicated that these effects might be marginal 40 and there is a high degree of uncertainty in the prediction of these costs. Instead, we have addressed this sensitivity by changing the growth rates (see below) by ±50% as open loop scenarios, which would cover a number of changes in transport volumes including those arising from demand suppressing costs increases. These assumptions lead to a scenario where 1/3 of the fuel used in 2100 is assumed to be SAF. We consider two different pathways of achieving the Flightpath 2050 objectives, late and continuous (FP2050 and FP2050-cont). Both scenarios have the same transport volume as BAU and consider technological improvements by 2050, which are formulated as ‘CO 2 emissions per passenger kilometre have been reduced by 75%, NO x emissions by 90% and perceived noise by 65%, all relative to the year 2000.’ 41 .

In addition to these five main scenarios, we introduce three possible development pathways related to the COVID-19 pandemic by varying the timing and degree of recovery (see main text).

Bottom-up-scenario building

In the Bottom-up scenario building, we present possible different development pathways and analyse how those scenarios influence the contribution of future aviation to climate change. Evolutionary technology scenarios are developed by expert judgement (TU-Delft, Chalmers, DLR, TU-Hamburg) with comprehensive knowledge on the possible availability of advanced technologies in future aircraft programmes along with in-house tools and models for engine performance, aircraft design and aircraft performance (explained in detail within the Supplementary Material). We assess a broad spectrum of possible aircraft configurations, technologies, systems and procedures currently under research and development and evaluate their viability and provide best estimates on fuel consumption and NO x emission reduction potentials (Table  3 ). Comparing with the work by Schäfer et al. 42 , the improvement rates are quite similar when matching our 2035 single-aisle aircraft with the evolutionary year 2035 configuration presented by Schäfer et al. The reference used in our paper is more recent and is comparable to Schäfer’s ‘intermediate’ aircraft. They predict an 18% fuel burn reduction of the evolutionary aircraft over the intermediate aircraft, which is similar to that obtained in our analysis. In a similar approach, Hileman et al. 43 investigated at the US domestic market considering single-aisle aircraft, only. According to them, a double bubble fuselage design 44 with lower cruise speed would have 42% lower fuel consumption when compared to B737-800, which is an older generation of aircraft than the A320neo. However, it is less likely that the next generation of single-aisle aircraft will deviate from a tube and wing geometry.

In this work, the fuel efficiency and emission analysis are done for both single-aisle and twin-aisle aircraft market segments, as those two segments will account for about 95% of globally available seat kilometres. Single-aisle aircraft serving short and short-to-medium distance routes are responsible for 47% of the worldwide aviation fuel consumption. Single-and twin-aisle aircraft serving the medium and long-range routes are responsible for another 47% of the fuel consumption. Hence, differently to the top-down FP2050 scenarios, we analyse possible future technology developments and derive the expected fuel efficiencies and NO x emission evolutions in a bottom-up approach and combine that with the same overall scenario definition as for the top-down scenarios, e.g. with respect to transport volume.

We compute emission inventories based on global fleet forecast data developed in the WeCare project 22 for the years 2015–2070, in 5-year steps, for single-aisle and twin-aisle market segments. As a simplification, we assume that for each segment there is one representative aircraft type which can be used to model the entire market segment appropriately, while multiple aircraft generations are considered. The aircraft Airbus A320neo and A350 are selected as best of class for the current generation and serve as reference aircraft types for the single-aisle and twin-aisle markets, respectively. Entry into service year of the current generation is assumed to be around 2015. The next generations of single-aisle aircraft are assumed to be conventional tube-and-wing configurations entering into service in 2035 and 2050 with the fuel consumption and NO x emission improvement factors as shown in Table  3 relative to the reference aircraft. For the twin-aisle market, we estimate the next generation aircraft entering into service in 2035 being a tube-and-wing configuration. In 2050, three different options, viz. a conventional tube-and-wing widebody aircraft, an aerodynamically improved aircraft, the so-called Flying-V or multi-fuel blended wing body (MF-BWB) with an advanced turbofan engine, both developed by TU Delft, and NASA’s N3-X blended wing body with a turbo-electric propulsion system, are considered and used as possible twin-aisle aircraft configurations. For each of the years considered, the actual fleet composition is calculated considering a fleet diffusion of the new aircraft generations, i.e. introducing and partly replacing old aircraft. The market penetration of an aircraft generation is modelled as an S-curve applying the Bass diffusion model that has been calibrated to reach >95% market penetration within roughly 15 years, which is a typical diffusion time for new aircraft 45 , 46 , starting from their respective entry into service (EIS) [2015, 2035, 2050].

For the calculation of the reference emission inventories (those based on the reference aircraft types), we apply the GRIDLAB methodology developed in DLR 47 . In a next step, those inventories are multiplied with the improvement factors (CO 2 and H 2 O inventories scaled according to fuel improvement, NO x inventory scaled according to NO x improvement) to determine the emissions for the respective aircraft generations. Finally, for all years, the corresponding emission inventory is obtained by combining the inventories of the individual aircraft types and generations according to their market share.

Climate modelling

We use the non-linear climate-chemistry response model AirClim 25 , 26 to analyse the climate impact of the various scenarios. AirClim is a surrogate model, which relies on a multitude of pre-calculated responses to emissions with a global climate-chemistry model and has been verified against reference models to correctly simulate scenarios, such as flying lower or higher 26 . AirClim considers changes in concentration of CO 2 , water vapour, ozone, methane and the formation of contrail-cirrus, and takes their lifetimes, effects on the Earth radiation budget and eventually the changes in the near-surface temperature into account. The spatial resolution of the relation between emission location and response depends on the kind of effect and related atmospheric lifetimes. For CO 2 , with a very long atmospheric perturbation, the emission location is unimportant and hence CO 2 concentration changes are simulated in a box model. The relation between emission location and chemical concentration changes largely depends on the altitude and geographical location of the emission. The lifetime of aviation NO x and aviation ozone is in the order of several weeks and months, respectively 48 . Accordingly, chemical responses are dependent on emission altitude and latitude, whereas for short-term contrail-cirrus effects, the longitude is also taken into account. As a background atmosphere, we take the RCP2.6 scenario into account, assuming a world which tries to achieve the Paris Agreement. The effect of sustainable aviation fuel on contrail-cirrus properties is taken into account by utilising the results from Moore et al. 49 and Burkhardt et al. 16 : A linear scaling between SAF use and reduction of soot number particle emissions is assumed, taking into account the results from measurements, which indicate that a 50–50 blend reduces the number of emitted soot particulates by 50% 49 and the change in contrail-cirrus properties and lifetime changes the contrail-cirrus RF following the results of Burkhardt et al. 16 by parameterising their results in their Fig.  1f :

where \(\triangle {{RF}}^{{contr}}\) is the relative change in contrail-cirrus radiative forcing (dimensionless value between 0 and 1) and Δ pn the relative change in particle number emissions (dimensionless value between 0 and 1). Note that the formula is only valid for Δpn \(\ge 0.1\) .

The effect of SAF use on contrail-cirrus properties and lifetime changes are qualitatively in agreement with Caiazzo et al. 50 . The increase in RF when using SAF in comparison to a kerosene baseline as calculated by Caiazzo et al. 50 stems from the increase in the calculated potential contrail-cirrus coverage, which is caused in their calculations by the change in the Schmidt-Appleman criterion.

Monte–Carlo analysis

Uncertainties in climate impact estimates are quantified by using a Monte–Carlo Simulation. As indicated in Lee et al. 7 , 28 the climate impact of aviation emissions upon the atmosphere is associated with large uncertainties. The approach has been tested in Dahlmann et al. 26 and successfully applied to obtain a robust climate impact for the mitigation option Flying slower and lower 51 . Here we categorise the uncertainties into three groups following Dahlmann et al. 26 : (1) uncertainty in atmospheric residence time ( ± 20%), (2) strength of RF ( ± 5% for CO 2 , ± 10% for CH 4 , and ± 50% for H 2 O, O 3 (incl. PMO), and contrail-cirrus), (3) relation between RF and near-surface temperature change (climate sensitivity parameter; ±5% for CO 2 , ± 10% for CH 4 and contrail-cirrus, ±30% for H 2 O and O 3 (incl. PMO)). Hence, we consider 11 uncertainty parameters, which are drawn individually for each simulation. A total of 10,000 simulations are performed to assess the uncertainty ranges, which are displayed in Fig.  4 for the top-down scenarios. A total of 3400 simulations combined with nine different ECATS scenarios resulting in 30,600 simulations are utilised for the Monte–Carlo analysis employed in the ECATS scenarios.

Data availability

The scenario data and result data are available on Zenodo 10.5281/zenodo.4627860.

Code availability

The code for deriving the scenarios is given in an excel spreadsheet and available on Zenodo 10.5281/zenodo.4627860. The software code AirClim is confidential proprietary information of DLR. Therefore, the code cannot be made available to the public or the readers without any restrictions. Licensing of the code to third parties is conditioned upon the prior conclusion of a licensing agreement with DLR as licensor. The codes used for analysing the data and plotting the analysed data are available from the corresponding author upon reasonable request.

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Acknowledgements

The authors like to thank Dr. Christoph Kiemle for providing an internal review. The non-profit ECATS-Association IASBL (Environmentally Compatible Air Transportation System, http://www.ecats-network.eu/ ) promotes and supports its Members’ joint activities and interests in the field of aviation and environmental impact. Its higher-level aim is to help making aviation sustainable. This study was launched and performed by ECATS members.

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Faculty of Aerospace Engineering, Delft University of Technology, Delft, Netherlands

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Volker Grewe, Arvind Gangoli Rao, Tomas Grönstedt, Carlos Xisto, Florian Linke, Joris Melkert, Jan Middel, Barbara Ohlenforst, Simon Blakey, Simon Christie, Sigrun Matthes & Katrin Dahlmann

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V.G. developed the paper idea, prepared the emission data excel sheet, and performed the AirClim simulations. A.G.R., T.G., C.X., F.L. and Jo.M. analysed the top-level objectives, gave advice on how to use them in the top-down emission calculation and developed the bottom-up scenario for technical improvements. Ja.M. and B.O. analysed the legislative objectives and advised on how to use them in the top-down emission calculation. S.B., S.C. and A.G.R. analysed the effects of SAF, their potential for future use, gave advice on how to use them in the top-down emission calculation and developed the SAF part of the bottom-up scenario. K.D. and S.M. supported the AirClim simulations and interpretation.

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Grewe, V., Gangoli Rao, A., Grönstedt, T. et al. Evaluating the climate impact of aviation emission scenarios towards the Paris agreement including COVID-19 effects. Nat Commun 12 , 3841 (2021). https://doi.org/10.1038/s41467-021-24091-y

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Air travel is a huge contributor to climate change. A new global movement wants you to be ashamed to fly.

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It was 2007, during a trip to visit her sister in Norway’s pristine Lofoten Islands , when Maja Rosén had an unsettling thought.

As she took in the breathtaking archipelago north of the Arctic Circle that is dotted with mountains, carved with fjords, and circled by sea eagles, she remembered she was looking at one of the fastest-warming regions of the planet.

And she realized that how she got there was part of the problem.

She’d carpooled with friends to Oslo from her home in Gothenburg, Sweden. The final leg was a short boat ride to the islands. And in between was a 500-mile flight from Oslo to Bodø.

For the distance, short flights produce a larger amount of greenhouse gas emissions per passenger compared to longer routes. That fact wasn’t something that struck her on her previous jaunts, like her flights to the United Kingdom to visit friends.

But upon basking in the fragile and sublime wonders of Lofoten, Rosén began to consider how her own actions might be threatening the region. The contradiction between her admiration for the scenery and her pollution from getting there, she decided, was too much to bear.

“It felt so wrong that my flight there was contributing to destroying that place,” Rosén, now 38, said. Soon after, she drastically curbed her flying, but in 2008, she concluded it wasn’t enough. “That’s when I decided not to fly again, and I have not regretted that decision,” she said.

Rosén has only become more alarmed and more determined to reduce emissions from air travel since then. Last year, she gave up her spot in medical school to focus on convincing other people to join her.

She founded a group called We Stay on the Ground in 2018 to recruit people to pledge to give up flying for one year. But the pledge only kicks in once 100,000 people in a given country have committed to doing the same. The threshold is a way to show participants that they’re not alone.

“For most people, it’s to know that others have made this decision. That’s really the most powerful way to make people change their minds,” Rosén said. So far, more than 8,000 people around the world have made the pledge.

Her effort may now be getting a boost from another Swede, 16-year-old climate change activist Greta Thunberg . She gained recognition when she went on strike from school last year to protest her government’s inaction on climate change, sparking a series of worldwide demonstrations, most recently the September 20 strike that drew an estimated 4 million people around the world.

But even after becoming a global celebrity, Thunberg has led by example, traveling to events around Europe mainly by train . She’s currently sailing from the US to Portugal to attend the UN climate meeting in Madrid in December.

Some Swedish airports have now reported a decline in travelers , which some activists attribute to the “ Greta effect ,” a newfound awareness of humanity’s impacts on the planet and a desire to make a difference.

The Swedes have even coined a word for the shame that travelers are beginning to feel about flying: flygskam , pronounced “fleeg-skahm.”

Rosén is trying to use flygskam to her advantage. She resolved last year to swallow her squeamishness about making her friends reckon with their own travel “because I sort of got fed up with being more scared of being socially inconvenient than climate collapse,” she said.

It’s not just Sweden; environmental activists, scientists who study the climate, and ordinary people in other countries like Switzerland , the United Kingdom , Germany , and the United States are curbing their air travel, if not giving it up outright.

However, the growing global alarm about the environmental impacts of aviation comes as air travel continues to rise. A record 31.6 million passengers are expected travel on US airlines this week for the Thanksgiving holiday, CNN reported . Our global economy is tightly interwoven with aviation as it carries goods and facilitates commerce. Leisure flights are also increasing, and growing demand for services like two-day and overnight shipping has led some companies like Amazon to invest more in cargo aircraft.

All this demand is expected to soar higher, particularly as prices for flights decline and wealth grows in emerging economies.

For regular flyers, air travel is often the dominant contributor to their greenhouse gas footprints. With the window rapidly closing to limit global warming to a bearable level — scientists warn that the planet has as little as 12 years to halve global emissions to restrict warming to 1.5 degrees this century — it is more critical than ever to find a way to shrink aviation’s carbon footprint. Every bit of carbon dioxide we emit now will linger in the atmosphere and warm the planet for decades, but completely decarbonizing aircraft will likely require technologies that are decades away. Reducing the number of flights is one of the few surefire ways to curb emissions in the meantime.

But unlike many other activities that contribute to climate change, air travel serves a valuable social function. It gives remote towns a lifeline to critical fuels, food, and medicines. It helps families stay connected across continents. It opens the door to life-changing experiences.

So reducing air travel demands a difficult moral reckoning, even if we make the decision solely for ourselves. But activists like Rosén say these actions have consequences for the whole world, so we cannot afford to make them without forethought.

Flying’s growing effect on the environment

If you’re a regular flyer, odds are that your biggest single source of greenhouse gas emissions each year is air travel. It likely dwarfs the footprint of all the lights in your home, your commute to work, your hobbies, and maybe even your diet.

“Euro for euro, hour for hour, flying is the quickest and cheapest way to warm the planet,” said Andrew Murphy, aviation manager at Transport & Environment, a think tank in Brussels.

That’s alarming because humanity can only emit so much more carbon dioxide to limit warming this century to 1.5 degrees Celsius, the more ambitious goal under the 2015 Paris climate agreement. An international team of researchers last year reported that meeting this target would require halving global emissions by as soon as 2030 , reaching net-zero emissions by 2050, and even getting to negative emissions thereafter.

Right now, the world is flying in the opposite direction. Global emissions reached a record high last year, and so did atmospheric concentrations of carbon dioxide .

Air travel is a big reason why. A one-way flight across the Atlantic from New York City to London emits one ton of carbon dioxide per passenger. There are upward of 2,500 flights over the North Atlantic every day.

And that’s just one air corridor. Around the world, aviation emits about 860 million metric tons of carbon dioxide every year, or about 2 percent of total global greenhouse gas emissions. Those numbers are poised to soar. The International Civil Aviation Organization projects that emissions from air travel will grow between 300 and 700 percent by 2050 compared to 2005 levels.

Those emissions in turn stand to have a devastating impact. The planet has already warmed by 1 degree Celsius since the dawn of the Industrial Revolution, which has caused rising seas and more frequent and intense heat waves. Every metric ton of carbon dioxide emitted leads to 3 square meters of Arctic sea ice loss . Aircraft also emit several other pollutants at altitude, like particulates, sulfur compounds, and nitrogen compounds, which have an additional warming effect. In some parts of the Arctic under busy air routes, these pollutants combined contribute one-fifth of the warming .

So the environmental costs of air travel are huge and growing, and the worst impacts will befall future generations. At the same time, there are very few options to limit those emissions except to not fly.

But that’s if you fly to begin with. In the United States, fewer than half of travelers in 2017 took a trip by air, according to an industry survey . Globally, less than one-fifth of the population has ever buckled in for a flight. That means a minority of frequent flyers contribute a disproportionate share of emissions. So reducing air travel is one of the most effective things individuals can do to shrink their carbon footprints.

Why flying is such a challenge for the environment

The fundamental problem behind decarbonizing air travel is the physics. To fly, you need an energy source that crams a lot of power into a small space, and right now, there is nothing as energy-dense as jet fuel , which has a specific energy of 11,890 watt-hours per kilogram.

Batteries aren’t even in the same airport. The best lithium-ion batteries top out at 265 watt-hours per kilogram , which is nowhere near enough get an airliner across the Pacific. The technology is improving, but one estimate shows that electrification of airliners will only start to make a dent in air travel emissions by midcentury.

At the same time, there is very little room left for making air travel more efficient. The current generation of jet engines is already closing in on its maximum efficiency. Fuel is also often the largest single expense for airlines, so they already face intense pressure to go farther with less.

One strategy to deal with aircraft emissions is to purchase credits or offsets. Many websites will calculate the emissions of your flight and sell you means to offset them, whether through planting trees that take up a given quantity of carbon dioxide or financing renewable energy projects to displace fossil fuels. But these offsetting programs are only as good as the accounting behind them, and for some, their effectiveness so far in limiting greenhouse gas emissions is questionable .

“The research shows that three-quarters of the offsets don’t deliver the reductions they claim to deliver,” said Anja Kollmuss, a policy analyst in Zurich who studies emissions trading.

Another option is to use a carbon-neutral fuel. Airlines are experimenting with biofuels derived from plants. Since plants recycle carbon that’s already in the atmosphere rather than introducing new carbon into the air, in theory, fuels derived from these crops have no net effect on the climate. In practice, it can be tricky to manage the energy balance of growing biofuels such that you aren’t expending more energy than you get out of them. Fuel crops also require land, and it’s not clear where all the land needed to sustain a wholesale shift of the global aviation industry will come from. Right now, biofuels are also expensive.

Yet another possibility is electrofuels . That’s where you use electricity to power a mechanism that stitches carbon dioxide from the air into longer molecules that can serve as fuels. However, it requires gobs of zero-emissions energy, and the technology is still in a gestational phase.

While there may be technology solutions for cutting the emissions for aviation in the future, there are few options available today beyond simply flying less. “We see this as individuals taking this into their own hands after governments have failed to act,” Murphy said.

Shorter flights have a disproportionately large carbon footprint

It takes a lot of energy to get a fully loaded airliner 6 miles into the air. On short flights, upward of 25 percent of the fuel used is consumed during takeoff.

Once at cruising altitude, though, the aircraft becomes much more fuel-efficient. That means longer, direct journeys have a smaller carbon footprint than shorter connecting hops. But only to a point.

For extremely long hauls, the extra fuel needed for the journey adds enough weight that the flight’s fuel efficiency is reduced, thereby increasing its carbon footprint per mile.

Depending on the aircraft and the route, there is an optimal distance for an air route that minimizes carbon dioxide emissions per passenger per mile — it follows a bathtub curve. One estimate from the Worldwatch Institute pegged the most fuel-efficient flight length at 2,600 miles, a bit longer than the distance between New York and Los Angeles.

But short-haul flights are increasing as countries like China, India, and Brazil open new routes to accommodate a voracious demand for domestic air travel.

Flying first-class also carries a larger carbon footprint, upward of three times larger than passengers in coach — partly because first-class seats are heavier and take up more floor space than cheaper sections of the aircraft.

A worldwide movement is growing. Sweden is its current epicenter.

Sweden is a somewhat odd place to emerge as the leader in flying shame and staying on the ground: It’s not the country with the most air travel or the highest per capita emissions . But in recent years, Swedish celebrities started pushing the idea into the mainstream. In 2015, Swedish Olympic biathlon gold medalist Björn Ferry committed to stop flying. Then in the fall of 2017, 10 Swedish celebrities published an article about deciding to no longer fly.

In 2018, the Swedish government began debating a tax on flying, and more national celebrities began to weigh in against air travel; the renowned Swedish writer Jens Liljestrand published a well-read article with the memorable title “I’m fed up with showing my child a dying world.”

The potential impacts of climate change also became startlingly vivid to many Swedes last year as an oppressive heat wave baked the country and dried out its forests. That heat helped fuel wildfires, with several igniting north of the Arctic Circle .

“It’s the first time Swedish people felt the consequences of climate change themselves,” Rosén said. “[L]ast summer was so dry and things were just looking yellow, and we were lacking water.”

Then in August 2018, Thunberg began her strike outside the Swedish parliament building, an action that soon launched her message worldwide.

Birgitta Frejhagen, 76, was so inspired by Thunberg that she founded a group called “Gretas Gamlingar” (Greta’s oldies). Her goal is to encourage older people to get involved in climate activism. She is currently aiming to recruit 10,000 Swedish seniors to participate in the World Action Day for the Climate on September 27 to coincide with a global youth climate strike .

Frejhagen noted that despite the alarm about the climate, flying is hard for Swedes like her to avoid. Many have family spread out over the large, sparsely populated country. Frejhagen broke her hip earlier this year, so long train or bus journeys are a painful ordeal.

“There is a shame of flying, but sometimes you have to fly,” she said.

Rosén said there isn’t anything unique in the Swedish soul that has made so many across the country so concerned about flying. “This could have happened anywhere,” she said. “We’ve had some good coincidences that have worked together to create this discussion.”

Nonetheless, the movement to reduce flying has created a subculture in Sweden, complete with its own hashtags on social media. Beyond flygskam, there’s flygfritt (flight free), and vi stannar på marken (we stay on the ground).

Rosén said that judging by all the organizing she’s seen in other countries, she thinks Sweden won’t long hold the lead in forgoing flying. “I wouldn’t be surprised if the Germans would follow us soon,” she said.

Scientists are having a hard time overlooking their own air travel emissions

Kim Cobb, a climate scientist at the Georgia Institute of Technology, has curbed her air travel by 75 percent.

“I really started thinking about my carbon footprint after Trump was elected,” she said. “Doing my climate science and donating to the right candidates was never going to be enough, even if you took that to scale.”

She created a spreadsheet to track her personal carbon footprint and found that flying formed the dominant share of her emissions. “By the end of 2017, 85 percent of my carbon footprint was related to flying,” she said.

Much of Cobb’s research — examining geochemical signals in coral to reconstruct historical climate variability — required her to travel to field sites in the equatorial Pacific.

While she doesn’t anticipate giving up those visits entirely, Cobb has taken on more research projects closer to home, including an experiment tracking sea level rise in Georgia. She has drastically reduced her attendance at academic conferences and this year plans to give a keynote address remotely for an event in Sydney.

I have begun replying to invitations “Due to the climate emergency, I am cutting down on air travel ...” Have been pleasantly surprised how many take up my offer of pre-recorded talk & Skype Q&A’s @GreenUCL @UCLPALS @UCLBehaveChange https://t.co/Hlxc4R6Lj3 — Susan Michie (@SusanMichie) June 29, 2019

Cobb is just one of a growing number of academics , particularly those who study the earth, who have made efforts in recent years to cut their air travel.

While she doesn’t anticipate making a dent in the 2.6 million pounds per second of greenhouse gases that all of humanity emits, Cobb said her goal is to send a signal to airlines and policymakers that there is a demand for cleaner aviation.

But she noted that her family is spread out across the country and that her husband’s family lives in Italy. She wants her children to stay close to her relatives, and that’s harder to do without visiting them. “The personal calculus is much, much harder,” she said.

She also acknowledged that it might be harder for other researchers to follow in her footsteps, particularly those just starting out. As a world-renowned climate scientist with tenure at her university, Cobb said she has the clout to turn down conference invitations or request video conferences. Younger scientists still building their careers may need in-person meetings and events to make a name for themselves. So she sees it as her responsibility to be careful with her air travel. “People like me have to be even more choosy,” she said.

Activists and diplomats who work on international climate issues are also struggling to reconcile their travel habits with their worries about warming. There is even a crowdfunding campaign for activists in Europe to sail to the United Nations climate conference in Chile later this year.

But perhaps the most difficult aspect of limiting air travel is the issue of justice. A minority of individuals, companies, and countries have contributed to the bulk of greenhouse gas emissions from flights and profited handsomely from it. Is it now fair to ask a new generation of travelers to fly less too?

Airlines and climate-concerned travelers

At least one airline is beginning to acknowledge the concern around flying. KLM CEO Pieter Elbers wrote in a letter in June that “we invite all air travellers to make responsible decisions about flying.” The letter showed no sign of the airline itself changing its ways, but the fact that KLM was even hinting at shaming its own passengers shows that climate concerns are difficult to ignore.

Cultural changes could become a big part of reshaping demand for air travel. Shifting tastes away from impressing friends with distant, Instagram-perfect destinations and more staycations could eventually yield some reductions in greenhouse gases from aircraft.

Transport & Environment’s Murphy also noted that for a long time, aviation fuels in many countries weren’t taxed, nor were their greenhouse gas emissions, so the aviation sector hasn’t faced the same pressure to decarbonize as the automotive industry. In fact, many countries directly and indirectly subsidize air travel, whether through tax breaks for aircraft manufacturers or government ownership of airlines. While this is slowly changing — France is set to introduce a new tax on airlines, for example — much more drastic policy action is needed to curb emissions from air travel.

However, targeting the consumers of goods and services rather than just their producers is a much more fraught political debate. It’s a more direct way of changing behavior and it shifts some of the costs directly to buyers, making the costs of curbing emissions much more visible, and contentious. Cutting consumption also brings up concerns about justice. Many activists argue that the heaviest burden of fighting climate change should be borne by large institutions rather than individuals. So while some airlines would prefer to embarrass their customers, climate campaigners say it’s the airlines themselves that should feel most ashamed.

Should you, dear traveler, feel ashamed to fly?

“Travel is fatal to prejudice, bigotry and narrow-mindedness, and many of our people need it sorely on these accounts,” wrote Mark Twain in The Innocents Abroad . “Broad, wholesome, charitable views of men and things can not be acquired by vegetating in one little corner of the earth all one’s lifetime.”

Air travel has yielded immense benefits to humanity. Movement is the story of human civilization, and as mobility has increased, so too has prosperity . Airplanes, the fastest way to cross continents and oceans, have facilitated this. And while some countries have recently retreated from the world stage amid nationalist fervor , the ease of air travel has created a strong countercurrent of travelers looking to learn from other cultures.

Compared to other personal concessions for the sake of the environment, reducing air travel has a disproportionately high social cost. Give up meat and you eat from a different menu. Give up flying and you may never see some members of your family again.

So it’s hard to make a categorical judgment about who should fly and under what circumstances.

But if you’re weighing a plane ticket for yourself, Paul Thompson, a professor of philosophy who studies environmental ethics at Michigan State University, said there are several factors to consider.

No need to tell me about your feelings of guilt. I see no reason for you to feel guilty. You already excel at ethical thinking in many other areas of your life and relationships. Judge for yourself what the times require of you, personally and politically. Act or don't act. — flyingless (@flyingless) July 17, 2019

First, think about where you can have the most meaningful impact on climate change as an individual — and it might not be changing how you are personally getting around. If advocacy is your thing, you could push for more research and development in cleaner aviation, building high-speed rail systems, or pricing the greenhouse gas emissions of dirty fuels. “That’s the first thing that I think I would be focused on, as opposed to things that would necessarily discourage air travel,” Thompson said. Voting for leaders who make fighting climate change a priority would also help.

If you end up on a booking site, think about why you’re flying and if your flight could be replaced with a video call.

Next, consider what method of travel has the smallest impact on the world, within your budget and time constraints. If you are hoping to come up with a numerical threshold, be aware that the math can get tricky. Online carbon footprint calculators can help.

And if you do choose to fly and feel shame about it, well, it can be a good thing. “I think it’s actually appropriate to have some sense of either grieving or at least concern about the loss you experience that way,” Thompson said. Thinking carefully about the trade-offs you’re making can push you toward many actions that are more beneficial for the climate, whether that’s flying less, offsetting emissions, or advocating for more aggressive climate policies.

Nonetheless, shame is not a great feeling, and it’s hard to convince people they need more of it. But Rosén says forgoing flying is a point of pride, and she’s optimistic that the movement to stay grounded will continue to take off.

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If Seeing the World Helps Ruin It, Should We Stay Home?

In the age of global warming, traveling — by plane, boat or car — is a fraught choice. And yet the world beckons.

By Andy Newman

The glaciers are melting, the coral reefs are dying, Miami Beach is slowly going under.

Quick, says a voice in your head, go see them before they disappear! You are evil, says another voice. For you are hastening their destruction.

To a lot of people who like to travel, these are morally bewildering times. Something that seemed like pure escape and adventure has become double-edged, harmful, the epitome of selfish consumption. Going someplace far away, we now know, is the biggest single action a private citizen can take to worsen climate change. One seat on a flight from New York to Los Angeles effectively adds months worth of human-generated carbon emissions to the atmosphere.

And yet we fly more and more.

[Read about how our Travel desk plans to address the environmental impact of its coverage.]

The number of airline passengers worldwide has more than doubled since 2003, and unlike with some other pollution sources, there’s not a ton that can be done right now to make flying significantly greener — electrified jets are not coming to an airport near you anytime soon.

Still, we wonder: How much is that one vacation really hurting anyone, or anything?

It is hard to think about climate change in relation to our own behavior. We are small, our effects are microscopically incremental and we mean no harm. The effects of climate change are inconceivably enormous and awful — and for the most part still unrealized. You can’t see the face of the unnamed future person whose coastal village you will have helped submerge.

But it turns out there are ways to quantify your impact on the planet, at least roughly. In 2016, two climatologists published a paper in the prestigious journal Science showing a direct relationship between carbon emissions and the melting of Arctic sea ice.

The square feet of Arctic summer sea ice cover that one passenger’s share of emissions melts on a 2,500-mile flight.

Each additional metric ton of carbon dioxide or its equivalent — your share of the emissions on a cross-country flight one-way from New York to Los Angeles — shrinks the summer sea ice cover by 3 square meters, or 32 square feet, the authors, Dirk Notz and Julienne Stroeve, found.

In February, my family of three flew from New York to Miami for what seemed like a pretty modest winter vacation. An online carbon calculator tells me that our seats generated the equivalent of 2.4 metric tons of carbon dioxide.

Throw in another quarter-ton for the 600 miles of driving we squeezed in and a bit for the snorkeling trip and the heated pool at the funky trailer-park Airbnb, and the bill comes to about 90 square feet of Arctic ice, an area about the size of a pickup truck .

When I did that calculation, I pictured myself standing on a pickup-truck-sized sheet of ice as it broke apart and plunged me into frigid waters. A polar bear glared hungrily at me.

Calculating the harm

And what of my vacation’s impact on my fellow man? Actually, academics have attempted to calculate that, too. Philosophers, not climatologists. But still.

In 2005, a Dartmouth professor, Walter Sinnott-Armstrong, wrote in a journal article provocatively titled “It’s Not My Fault: Global Warming and Individual Moral Obligations” that he was under no moral obligation to refrain from taking a gas-guzzling S.U.V. for a Sunday afternoon joy ride if he felt like doing so.

“No storms or floods or droughts or heat waves can be traced to my individual act of driving,” he wrote. Conversely, “If I refrain from driving for fun on this one Sunday, there is no individual who will be helped in the least.”

Other philosophers questioned his reasoning.

Professor John Nolt of the University of Tennessee took a stab at measuring the damage done by one average American’s lifetime emissions. (The average American generates about 16 metric tons of carbon dioxide-equivalent a year, more than triple the global average.)

Noting that carbon stays in the atmosphere for centuries, at least, and that a United Nations p anel found in 2007 that climate change is “likely to adversely affect hundreds of millions of people through increased coastal flooding, reductions in water supplies, increased malnutrition and increased health impacts” in the next 100 years, Professor Nolt did a lot of division and multiplication and arrived at a stark conclusion:

“ The average American causes through his/her greenhouse gas emissions the serious suffering and/or deaths of two future people.”

Then Avram Hiller of Portland State University used Professor Nolt’s approach to derive the impact of Professor Sinnott-Armstrong’s hypothetical 25-mile ride.

“At a ratio of one life’s causal activities per one life’s detrimental effects, it causes the equivalent of a quarter of a day’s severe harm,” he wrote.

“In other words, going for a Sunday drive has the expected effect of ruining someone’s afternoon.”

Multiply that joy ride by a three-person Florida vacation and you’ve ruined someone’s month. Something to ponder while soaking up UV-drenched rays on a tropical beach.

Ships? Even worse

There are alternatives to flying, of course. Perhaps a cruise? After all, there’s more ocean than there’s been in thousands of years. With the Northwest Passage now mostly ice-free in the summer, new vistas have opened. One cruise company runs polar bear tours to check out “the Arctic’s ‘poster boy.’”

Perhaps not. Bryan Comer, a researcher at the International Council on Clean Transportation, a nonprofit research group, told me that even the most efficient cruise ships emit 3 to 4 times more carbon dioxide per passenger-mile than a jet.

And that’s just greenhouse gas. Last year, an assistant professor at the Johns Hopkins Bloomberg School of Public Health found that the air onboard cruise ships was many times dirtier than the air nearby onshore .

The amount of carbon dioxide the most efficient cruise ship emits per passenger mile when compared with a jet.

“Some of the particulate counts were comparable to or worse than a bad day in some of the world’s most polluted cities like Beijing and Santiago,” said Kendra Ulrich of Stand.earth, the advocacy group that commissioned the study.

While most cruise ships run on highly polluting heavy fuel oil, many have begun using “scrubbers” to remove toxic sulfur oxides from their exhaust. But the scrubbers discharge these and other pollutants into the ocean instead, and they’ve been banned by seven countries and several U.S. states.

A spokeswoman for Cruise Lines International Association, a trade group, said that the scrubbers comply with the new 2020 standards for air and water quality set by the International Maritime Organization, a U.N. agency. The spokeswoman, Megan King, added that it was not fair to compare emissions from ships and jets because a jet is just a transportation vehicle while a cruise ship is a floating resort and amusement park.

There’s always driving, which is less carbon intensive than flying, especially if there are multiple passengers. But “less” is relative, and most long trips are out of practical driving range anyway.

Considering carbon offsets

Maybe there is a justification out there somewhere: Personal decisions alone won’t stop global warming — that will take policy changes by governments on a worldwide scale. Tourism creates millions of jobs in places starved for economic development. Carbon offsets can effectively cancel out our footprint, can’t they?

Carbon offsets do seem to offer the most direct way to assuage traveler’s guilt. In theory, they magically expiate your sins. You give a broker some money (not a lot of money either — carbon offsets can be bought for $10 per metric ton). They give it to someone to plant trees, or capture the methane from a landfill or a cattle operation, or help build a wind farm, or subsidize clean cookstoves for people in the developing world who cook on open fires. All these things help cut greenhouse gas.

But nothing is that simple in practice. Carbon-offset people talk about concerns with things called additionality, leakage and permanence.

Additionality: How do you know the utility would not have built the wind farm but for the money you gave them?

Permanence: How do you know the timber company that planted those trees won’t just cut them down in a few years?

Leakage: How do you know the landowner you just paid not to cut down an acre of rain forest won’t use the money to buy a different acre and clear that?

While certifying organizations go to great lengths to verify carbon offset projects, verification has limits.

“Whether someone would have planted trees anyway, or taken some other action like building a housing development, is ultimately unknowable and something you have to construct,” said Peter Miller, a policy director for the Natural Resources Defense Council and a board member of the Climate Action Reserve, the country’s biggest carbon offset registry. “It’s an endless debate.”

Some carbon offsets are surer bets than others. “With methane capture,” Mr. Miller said, “once you capture that methane and you burn it — you’re done. It’s not in the atmosphere, it’s not going in the atmosphere. You’ve got a credit that’s achieved and you’ve avoided those emissions forever.”

Not flying at all would be better, Mr. Miller said, “but the reality is that there’s lots of folks that are going to do what they’re going to do.” For them, offsets are a lot better than nothing.

But some climate experts call offsets a cop-out.

“It’s like paying someone else to diet for you,” said Alice Larkin of the University of Manchester’s Tyndall Centre for Climate Change Research, who has not flown since 2008.

She said that while governments do need to take tough action, they derive their courage to do so from the conduct of citizens. “In my idea, people move first,” she said.

Offsets, she said, encourage a break-even mind-set when what’s needed to avert disaster is to slash fossil-fuel consumption immediately.

Her colleague Kevin Anderson says that when you buy a ticket you’re not buying just a seat on a plane. You’re telling the aviation industry to run more flights, build more jets, expand more airports.

“Offsetting, on all scales, weakens present-day drivers for change and reduces innovation towards a lower-carbon future,” Professor Anderson wrote in 2012 . Lately, a grassroots anti-flying movement has been gathering momentum in Europe, particularly Scandinavia.

But the world still beckons

I’d like to be able to tell you that knowing what I’ve learned reporting this piece, I have sworn off long-distance travel.

But actually this summer, we’re going to Greece , with a stopover in Paris . Carbon footprint of plane tickets: 10.6 metric tons, enough to melt a small-apartment-size d piece of the Arctic.

The increase in airline passengers worldwide since 2003.

We committed to going months ago, but I suspect we would make the same choice today. We’re going because last year we canceled vacation to come home and watch our dog die. We’re going because the New York City public high school application process was an ordeal.

Mostly we’re going because of things we saw last time we were there. The tiny beach at the base of the towering cliff. The playground where the little children played past midnight while their parents and grandparents sat chatting. Chubby partridges pecking around the ruined temple of Poseidon.

Before we go, we will buy enough offsets to capture the annual methane emanations of a dozen cows — that’s several times what is needed to balance out the carbon effects of our flights. May they help keep a polar bear afloat.

Andy Newman is a Metro reporter for The New York Times.

Follow NY Times Travel on Twitter , Instagram and Facebook . Get weekly updates from our Travel Dispatch newsletter, with tips on traveling smarter, destination coverage and photos from all over the world.

Andy Newman has covered New York City and vicinity for The Times since 1997. He was the founding reporter of the Pet City and New York Today columns and ran The Times's City Room blog. More about Andy Newman

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Reducing environmental impact crucial to airline industry’s survival, experts say.

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This story is part of a CBC News series entitled  In Our Backyard , which looks at the effects climate change is having in Canada, from extreme weather events to how it's reshaping our economy.

Taking a plane may be the fastest way to travel, but it puts a lot of climate-changing emissions into the air.

Concern about aviation's carbon footprint has prompted Swedish teen activist Greta Thunberg and others to publicly give up flying altogether as part of the "flygskam" or "flight shame" movement.

Even airlines are questioning whether people should fly so much. KLM suggests people take the train when possible, while Lufthansa's CEO criticized Ryanair's cheapest flights, which are less than $15 Cdn, as " economically, ecologically and politically irresponsible ."

"We know that aviation is an outsized share of emissions and it's one of the largest sort of personal type of carbon dioxide emissions that an individual can emit," says Ryan Katz-Rosene, a University of Ottawa professor who studies sustainable transportation. He has cut back to one flight a year and is reducing the distance he flies due to concerns about environmental impacts.

Air travel is responsible for about two per cent of global CO2 emissions. If aviation were a country, that would put it among the top 10 emitters in the world .

And its environmental impact is far greater — about 4.9 per cent of the total human contribution to global warming — due to the nitrogen oxides, contrails and cirrus clouds it generates in the atmosphere that have a further warming effect. 

To make matters worse, aviation emissions are growing fast. Worldwide, passenger numbers are expected to double to 8.2 billion by 2037, the International Air Transport Association  predicts .  By 2050, without intervention, annual aviation emissions could be more than six times higher than in 2010 , says the UN-backed International Civil Aviation Organization.

"It's not really sustainable the way we do it, in terms of CO2 emissions especially," says David Zingg, professor and director of the Centre for Research in Sustainable Aviation at the University of Toronto.

He believes that lack of sustainability is "by far the biggest threat to aviation's future."

In Sweden air travel is down 4,5% in first quarter 2019. That’s almost 400000 less passengers. <br>Despite growing economy. The experts are puzzled... <a href="https://twitter.com/hashtag/IStayOnTheGround?src=hash&amp;ref_src=twsrc%5Etfw">#IStayOnTheGround</a> <a href="https://twitter.com/hashtag/ClimateJustice?src=hash&amp;ref_src=twsrc%5Etfw">#ClimateJustice</a> <a href="https://twitter.com/hashtag/ClimateBreakdown?src=hash&amp;ref_src=twsrc%5Etfw">#ClimateBreakdown</a> <a href="https://t.co/iw3hZYhSDu">https://t.co/iw3hZYhSDu</a> &mdash; @GretaThunberg

So is reducing or eliminating air travel the only solution?  

Zingg, who has spent years researching how to make flying greener, doesn't think so. He believes it should be feasible in the future to reduce the impact per passenger per kilometre travelled to one-eighth of what it is today — an amount he considers a "negligible part of the human contribution" to climate change.

Here's a look at some ways to make that happen.

1. Improve aircraft efficiency through technology

Jet aircraft use 80 per cent less fuel per seat per kilometre today than they did in the 1960s, according to Air Transport Action Group, which is funded by and represents the air transport industry. But efficiency gains aren't keeping pace with the growth in passengers and the distance travelled, so overall emissions are rising.

Zingg says beyond improving the engine there are two key ways to improve aircraft efficiency. 

One is reducing weight, largely through the use of lighter materials — a strategy used by Solar Impulse 2, the solar plane made of lightweight carbon fibre  that flew around the world in 2016.

The other is reducing drag, Zingg's own area of research. His lab is looking into more streamlined aircraft designs that make the plane look "a bit like a flying wing." Another option is bracing the wings with a truss that allows planes to have a longer wingspan — another strategy used by Solar Impulse 2.

2. Electrification and alternative fuels

Planes emit CO2 by burning fossil fuels, so an obvious solution is powering them with cleanly sourced electricity instead. A number of companies are working on small electric planes, including Richmond, B.C.-based Harbour Air, which flies tour and charter seaplanes along the coast of B.C. and Washington state. It aims to have a fully electric prototype in the air by November, founder and CEO Greg McDougall said.

International competitors include U.S..-based Wright Electric and Israel-based Eviation, which plan to test all-electric nine-seater planes later this year with ranges of up to 1,000 kilometres. 

Airbus is working on the E-Fan X hybrid-electric jet , based on the BAE 146, which holds about 100 passengers. It will replace one of four jet engines with an electric motor and aims to fly short-haul flights starting in 2021.

Lindsay, Ont.-based Horizon Aircraft is also working on a prototype of a five-seater hybrid-electric plane that runs on batteries and regular gasoline instead of jet fuel, with a range of 1,500 kilometres.

Unfortunately, about 80 per cent of the airline industry's emissions come from passenger flights longer than 1,500 kilometres , according to the Air Transport Action Group. And Zingg says because planes are so weight-sensitive and batteries still so heavy, larger electric aircraft are "not on the horizon." 

How the aviation industry is going green

That's led researchers to consider another option — replacing fossil fuel-based jet fuel with alternative fuels, such as biofuels derived from plants. Plants absorb CO2 as they grow, potentially reducing net emissions by up to 80 per cent, the industry says . 

It's something airlines have experimented with. For example, last year a Qantas flight flew from the U.S. to Australia using a blend of 90 per cent jet fuel with 10 per cent mustard seed-based biofuel from Gatineau-based Agrisoma Biosciences Inc.

Air Canada has also experimented with biofuel .

But there are two hurdles to scaling up biofuel's use, Zingg says: 

Getting a stable supply that doesn't displace food production.

Producing enough to supply the airline industry.

Solving those challenges is "progressing quite slowly," he added. "Many of us hoped we would already have more biofuel in the system by now."

3. Target airports

Ever been on a flight that circled a congested airport waiting for a spot to land? According to the Intergovernmental Panel on Climate Change (IPCC), improvements to air traffic management and other operational procedures could reduce aviation fuel burn by up to 18 per cent . So could reducing things like taxiing on the ground. 

In fact, planes even burn jet fuel or diesel while sitting at the gate — for lighting, heating and air conditioning. And many airport vehicles, such as those used for refuelling and transporting passengers and luggage, also burn fuel. All those things could be electrified.

Vancouver International Airport says it has cut greenhouse gas emissions by nearly 30 per cent since 2007 despite serving 8.5 million more passengers, by electrifying its ground fleet, investing in more energy efficient airfield and apron lighting and making buildings more energy efficient.

Other Canadian airports, including Calgary, Montreal and Winnipeg, have introduced a small number of electric vehicles.

There are also non-technical ways to make flights more efficient — making sure planes are fuller, carry less luggage (by charging more for it) and maybe even reducing weight by eliminating in-seat entertainment screens, Zingg says: "When you're actively looking for one or two per cent [reduction in weight], those kinds of things are annoying."

4. Regulation, policies and economic tactics

Increased efficiency "will not fully offset the effects of the increased emissions resulting from the projected growth of aviation," says the IPCC.

It suggests also using regulatory options such as:

• Stringent aircraft emissions regulations. 
• Removal of subsidies and incentives that have negative environmental consequences. 
• Environmental levies. 
• Emissions trading.

All of these are expected to increase the price of plane tickets, which may in turn discourage people from flying.

In 2017, the International Civil Aviation Organization (ICAO), the UN's aviation agency, set a new CO2 emission standard for new aircraft.

Zingg said that while it isn't ambitious right now, that's a "huge step" for the industry, and it could potentially set stricter targets in the future.

The EU has been including aviation emissions in its emissions trading system since 2012, which it estimates has reduced the carbon footprint of aviation by more than 17 million tonnes per year.

• What on Earth? Air travel emits a lot of carbon, but there are ways to fly more responsibly
• CBC explains Carbon offsets: Worth buying to fight climate change?

Katz-Rosene, who has been doing research on CORSIA, calls it "a very hollow agreement."

"The entire premise of CORSIA is to facilitate or to enable the sector to continue growing," he said, "which is ultimately the fundamental problem with aviation emissions."

He notes that, generally, economic incentives to fly are the opposite of what they should be, given the environmental harm. Frequent flyers are showered with perks, and people earn "air miles" as they shop, with a flight held up as the "ultimate reward."

"We have a system that rewards air travel," he said, "and that shouldn't be the case."

He thinks not just governments, but businesses and institutions that require workers to fly, need to rethink their travel policies to tackle the problem.

5. Fly less

And, like Thunberg and other promoters of the "flygskam" movement, Katz-Rosene thinks flying less is part of the solution, along with technology and regulation.

"I think we need an all hands on deck approach, really," he said.

If you must fly, there are some ways to reduce the impact of your flight , but they make a small difference compared to staying on the ground.

• Fighting climate change may be cheaper and more beneficial than we think
• Best way to fight climate change? Plant a trillion trees

"Certainly, not flying as much would reduce the CO2 emissions from aviation," acknowledges Zingg. But he said his goal and that of the industry is to make it possible to fly more sustainably.

"If the only solution is to stop flying, then I would say people like me have kind of failed."

As for the other solutions: "None of them will do it all by themselves.… The really important thing is to do it all."

Corrections

• An earlier version of this story stated that David Zingg said the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) isn't ambitious right now, but is still a "huge step" for the industry. In fact, he was not referring to CORSIA, but to the International Civil Aviation Organization's CO2 standard for new aircraft. Aug 13, 2019 1:25 PM ET

ABOUT THE AUTHOR

Science, climate, environment reporter

Emily Chung covers science, the environment and climate for CBC News. She has previously worked as a digital journalist for CBC Ottawa and as an occasional producer at CBC's Quirks & Quarks. She has a PhD in chemistry from the University of British Columbia. In 2019, she was part of the team that won a Digital Publishing Award for best newsletter for "What on Earth." You can email story ideas to [email protected].

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With files from Laura MacNaughton

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Flight Shaming: Is Flying Bad for the Environment?

As people become more conscious of their environmental impact on the world, there’s been an increased focus on air travel — and, over the past couple of years, a corresponding increase in “flight shaming.” The term is coined from the Swedish flygskam , which means “flight shame” i.e. you personally feel shame about flying but, unsurprisingly, it has devolved into shaming others for flying due to its carbon footprint.

After all, there is no denying that flying increases your personal carbon footprint — a lot. My carbon footprint is undoubtedly through the roof because of all my intense flying habits.

But what can we do? And is focusing on this issue really the best use of our efforts? Just exactly how bad is flying really?

Air travel accounts for 2.5% of global carbon emissions . In the US, flying accounted for 8% of transportation emissions , but less than 3% of total carbon emissions. It’s a drop in the bucket when compared to other industries in the United States:

• Transportation: 27%
• Electricity 25%
• Industry 24%
• Commercial/Residential 13%
• Agriculture 11%

So, when looking at the math, flying isn’t really the worst climate offender out there. There are far worse industries out there. Shouldn’t we focus on them?

Cutting down carbon emissions from flying isn’t going to make a big dent in total emissions.

And you can’t just shut off air travel. The world economy relies on it to function. We live in a globalized economy — and benefit from that — because of air travel. Ending all flights would end our modern economy.

Moreover, there are instances where flying is required. I mean, are we going to take boats across the ocean all the time? What if we have to rush to a sick loved one’s side? Driving might take too long.

Not only that, but even if we all cut back on our flying — as we did during COVID — the industry itself will still fill the gap. Policies are in place that require flights to happen regardless of who is flying. In the winter of 2021, for example, Lufthansa alone flew over 21,000 empty flights (known as “ghost flights”) just to maintain its airport slots. (Due to the shortage of airports, airlines compete for spots at airports and need to maintain a certain threshold of flights to keep those spots).

With all that in mind, it seems that we could get bigger wins elsewhere. I mean, just eliminating ghost flights alone would be the equivalent of removing 1.4 million cars from the road.

But I’m not a scientist. So I called one up to ask about the environmental impact of air travel.

Michael Oppenheimer is a professor at Princeton University, co-founded the Climate Action Network , and has been a leading scientist on climate change for over 30 years. He was one of the principal participants of the Intergovernmental Panel on Climate Change. He said:

If you’re a traveler, you have to worry about four things from aviation. One is just the carbon dioxide emissions…number two, you have to worry about the fact that particulate matter from jets can provide surfaces for the formation of clouds, and that that reflects some sunlight…the third thing would be…the production of tropospheric ozone [a greenhouse gas] through the emission of nitrogen oxides…and then there’s a fourth thing, which is that high-flying jets that actually enter the stratosphere can produce some…ozone, and at some altitudes, they may release particulate matter, which would encourage the destruction of ozone.

My conversation with Prof. Oppenheimer gave me pause. It’s just not our carbon footprint we need to worry about when we fly, which makes the total cost of our flights pretty bad. (But, since the carbon effect is the easiest documented, we’re going to focus on that here.) Further research showed that flying is pretty bad.

Most of the time.

While you can say that, generally speaking, flying is worse than any other mode of transportation, the science is tricky because, since there is a surprising number of variables, there’s really no good apples-to-apples comparison. Depending on the make, model, distance, and the number of passengers in your car, driving might be better — or worse — than flying. The same is true with a bus. How many passengers are on that bus? Is it gas-powered or electric?

According to the International Civil Aviation Organization (ICAO) , a round-trip flight from NYC to LA produces 1,249 lbs. (566.4 kg) of carbon per person. A car getting an average of 20 miles per gallon produces 4,969.56 lbs. (2,254.15 kg) for the same trip for one person. 1

If you’re driving alone, especially over a long distance, it might better to fly. Yet, on that same trip, if you carpool with three other people, you can get your numbers down by a fourth, making driving the better option.

So it turns out there’s no one-size-fits-all answer. You can’t say “flying is bad, never fly” because sometimes it’s better to fly.

That said, a round-trip flight from Paris to London creates 246 lbs (111.5 kg) of carbon while taking the Eurostar (train) will create about 49 lbs (22.2 kg) of carbon .

From Vienna to Brussels, a flight creates 486 lbs (220.4 kg) while the new night train (which takes around 14 hours) creates 88 lbs (39.9 kg) per person .

The International Council on Clean Transportation also came to the same conclusion when they looked into it. It turns out figuring out what mode of transport is quite complicated. As you can see from their chart, no one transportation option is the best every time:

So what’s a traveler to do? I felt overwhelmed just researching this article and doing the math on all these example trips. I didn’t realize how complex this was. And, as I explain later, depending on the carbon calculator you use, your numbers can vary wildly.

So what can you do?

Here are some tips I learned in this process to help reduce the carbon footprint of flying:

1. Avoid short-haul flights – Multiple reports, including from NASA and The University of San Francisco have shown that a significant portion (an estimated 10-30%) of airplane emissions occur during takeoff and landing. This means that if you take a lot of short-haul flights, you tend to have a higher per-pound footprint. Flying nonstop rather than a bunch of connecting flights is the better option environmentally.

The longer the distance, the more efficient flying becomes ( because cruising altitude requires less fuel than any other stage of flying ). If you’re flying a short distance, consider driving or taking a train or bus instead.

2. Buy carbon offsets (or don’t actually) – Carbon offsets offer a way to balance out your pollution by investing in projects that reduce emissions of carbon dioxide or other greenhouse gases in the atmosphere. If you used one ton (2,000 pounds) of carbon, you can support a project like planting trees or clean water initiatives that would produce a saving in carbon equal to what you use (so the scale balances).

Websites such as Green-e , Gold Standard , and Cool Effect can give you a list of good projects to support.

But, while these programs help, they aren’t super effective. For example, it takes 15-35 years for trees to grow big enough to capture carbon.

And carbon offsets just shift the burden of what you’re doing to somewhere else. It’s not an actual reduction in carbon emissions; you’re just investing in something that you hope will take as much out as you put in.

In fact, in a 2017 study of offsets commissioned by the European Commission found that 85% of offset projects under the Kyoto Protocol’s Clean Development Mechanism (CDM) had failed to reduce emissions.

Much of my conversation with Prof. Oppenheimer centered on carbon offsets. He said,

Offsets are good if, and only if, they’re accountable, that is, you’re sure they’re producing the greenhouse gas benefit that they’re advertised at, and that’s sometimes hard to figure out because the emissions are not direct, they’re somewhere else…so, you want to only do offsets and count that as part of your greenhouse gas budget if they’re from an accounting system that’s comprehensive and reliable. Secondly, offsets are good if some have been designed to stimulate technological change or other changes that would not have happened so easily without the offset.

He also said that he could “imagine situations where offsets are fine, even beneficial, but there are a lot of situations where they are not and where they’re…far worse than doing the reduction at…the direct emission site.”

I think this is the point. Offsets don’t have strict controls, so you don’t know if they are really working. And it’s far better to force more efficiency from airlines and build up alternatives to flying in the first place. Much of my research showed that offsets, while making you feel good, aren’t as effective as fighting for reductions directly at their source.

So, you can buy them, but be really careful and do your research into the projects you’re supporting.

3. Fight for better flying – We need to put pressure on airlines to improve fuel efficiency through new aircraft designs and operations, like implementing the usage of biofuels and planes that run on clean electricity, plus modernizing their fleets. For example, the new Dreamliner has very fuel-efficient engines that reduce CO2 emissions by about 20% in comparison to the planes it replaced. Pressure airlines and fly newer, more fuel-efficient planes when you can. Additionally, try to fly an airline that is generally fuel-efficient.

4. Calculate your footprint – As we’ve seen, sometimes it’s better to fly. Sometimes it’s not. Use a carbon calculator for your trip to see which mode of transportation has the lowest carbon footprint for your trip. If flying is a bad option, look for alternatives like trains, ridesharing like BlaBlaCar, or the bus. Some suggested carbon calculators are:

• CarbonFootprint.com

However, I want to put a big caveat here. My team and I used a lot of calculators for this article. We each found a bunch and tested them ourselves to see if our numbers matched. Like peer review scientific papers, we kept checking each other’s work. We were incredibly shocked to find out just how much variation there was between the carbon calculators. My suggestion is to use multiple calculators to find out what your exact footprint is.

Prof. Oppeniemer concurred, saying, “If the calculator shows that the car is worse, I would believe that, because all this is very sensitive to the load factor. And also…since a lot of fuel is burned on takeoff and landing, the longer the flight, you may sort of amortize the trip if you’re in an airplane.”

5. Fly less – At the end of the day, flying less is the best way to reduce your carbon footprint. Taking lots of flights a year, even if you do some of the lifestyle changes we mention below, is still going to cause your personal footprint to be huge.

In fact, the majority of emissions come from just 1% of travelers — avid fliers who take multiple flights per month. So, if you’re only taking a couple flights per year for your standard vacation, you shouldn’t beat yourself up. There are worse offenders out there who we should be focusing on.

I think we should all fly less. I look for ways to fly less all the time. We all need to be more aware of our carbon footprint. But it’s also important to understand, total flight emissions are small compared to other industries. There are so many factors that go into personal carbon footprints that I think we can make a bigger difference through the day-to-day actions we take since, as we’ve seen, most industries have a bigger impact on emissions! Do things like:

• Buy things that last a long time
• Buy secondhand
• Buy local, not online (so much packaging waste)
• Reduce your plastic consumption
• Switch to a hybrid or electric car
• Eat less takeout to avoid the plastic and other waste that comes with it
• Eat less meat or go vegetarian or vegan
• Switch your home heating to renewable energy
• Change your incandescent light bulbs to LEDs
• Install low-flow showerheads and toilets

If you don’t fly a lot generally, the things you do every day can have a huge impact on your carbon footprint and help the environment. Let’s not lose the forest through the trees.

In today’s “cancel culture,” we’re all supposed to be perfect people — but those who cast the most stones are imperfect too.

We all are.

I don’t believe in flight shaming because, when does shaming someone ever work?

When people feel like their values are attacked, they harden their positions. If you shame someone, they will just do more of the same and become entrenched in their positions. Study after study has shown this to be true.

Telling the person they are bad — when no one ever wants to think of themselves as a bad person — won’t get you anywhere.

That’s not how human psychology works.

Instead, I believe in finding and presenting alternatives.

That’s how you affect change.

I’m not going to judge people who fly. Nor will I judge people who have decided the best way to live their values is to fly less.

If you’re worried about the environmental impact of flying, reduce your own footprint, educate your friends on why they should fly less and find alternative transportation, and contribute to some good organizations that are out there fighting for a greener world:

• 1% for the Planet
• Alliance for Climate Education
• Alliance to Save Energy
• Environmental Defense Fund
• Greenpeace USA
• Natural Resources Defense Culture
• Ocean Conservancy
• Pew Charitable Trust
• Union of Concerned Scientists

The world needs immediate climate action. And there’s a lot you can do to help. If you want more effective change, donate to NGOs and sociopolitical groups that are pushing climate crisis action immediately — because the longer we wait, the worse it will get.

Support green-energy projects.

Fund the planting of trees.

Donate to land reclamation.

Vote for politicians that support climate action.

Fast action will get you more bang for your buck than anything else.

But whatever you do, don’t shame people for flying. That’s not going to do anything.  

Book Your Trip: Logistical Tips and Tricks

Book Your Flight Find a cheap flight by using Skyscanner . It’s my favorite search engine because it searches websites and airlines around the globe so you always know no stone is being left unturned.

Book Your Accommodation You can book your hostel with Hostelworld . If you want to stay somewhere other than a hostel, use Booking.com as it consistently returns the cheapest rates for guesthouses and hotels.

Don’t Forget Travel Insurance Travel insurance will protect you against illness, injury, theft, and cancellations. It’s comprehensive protection in case anything goes wrong. I never go on a trip without it as I’ve had to use it many times in the past. My favorite companies that offer the best service and value are:

• SafetyWing (best for everyone)
• Insure My Trip (for those 70 and over)
• Medjet (for additional evacuation coverage)

Want to Travel for Free? Travel credit cards allow you to earn points that can be redeemed for free flights and accommodation — all without any extra spending. Check out my guide to picking the right card and my current favorites to get started and see the latest best deals.

Need Help Finding Activities for Your Trip? Get Your Guide is a huge online marketplace where you can find cool walking tours, fun excursions, skip-the-line tickets, private guides, and more.

Ready to Book Your Trip? Check out my resource page for the best companies to use when you travel. I list all the ones I use when I travel. They are the best in class and you can’t go wrong using them on your trip.

Sources : We did a lot of research for this post. While we linked to some in our articles, here are some of the other sources we used for this post:

• https://www.yaleclimateconnections.org/2015/09/evolving-climate-math-of-flying-vs-driving/
• https://www.epa.gov/greenvehicles/
• https://calculator.carbonfootprint.com/calculator.aspx?tab=4
• https://www.icao.int/environmental-protection/CarbonOffset/Pages/default.aspx
• https://www.nature.com/news/the-inconvenient-truth-of-carbon-offsets-1.10373
• https://www.bbc.com/news/science-environment-49349566
• https://www.vox.com/the-highlight/2019/7/25/8881364/greta-thunberg-climate-change-flying-airline
• https://www.mic.com/articles/192792/how-to-reduce-your-travel-carbon-footprint-on-your-next-trip

Got a comment on this article? Join the conversation on Facebook , Instagram , or Twitter and share your thoughts!

Disclosure: Please note that some of the links above may be affiliate links, and at no additional cost to you, I earn a commission if you make a purchase. I recommend only products and companies I use and the income goes to keeping the site community supported and ad free.

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Impact of air travel

The continued growth in popularity for air travel has made aviation one of the fastest growing sources of greenhouse gas emissions with the International Council on Clean Transportation (ICCT) reporting a 32% increase in CO 2 emissions since 2013. If current trends continue, aviation could be responsible for consuming a quarter of the 1.5°C carbon budget by 2050.

Increasingly, tourists are taking longer flights than most business travellers. What’s more, these emissions are released directly into the upper atmosphere where they cause far more damage, and more rapidly, than if released at ground level. Thus, taking the train to Paris instead of flying effectively cuts CO 2 emissions by 90%. Given how hellish airports are these days this is an increasingly popular option.

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The impact of air travel on the environment: can your next flight make a difference?

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• Car with one passenger – 171g
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• Domestic rail – 41g
• Coach – 27g
• Eurostar – 6g

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Passing Thru Travel

12 Best Practices for Sustainable Travel in 2024 – How to Travel with Minimal Environmental Impact

Posted: February 14, 2024 | Last updated: February 14, 2024

In an era where climate change and environmental conservation are paramount, sustainable travel has become more than a buzzword—it’s a necessary shift in how we explore the world. Sustainable travel means being mindful of our environmental impact while experiencing new cultures and destinations. This guide delves into the best practices for eco-friendly travel, ensuring your adventures contribute positively to the planet and local communities.

Choose Eco-Friendly Transportation

When planning your travels, opting for transportation methods that minimize carbon emissions is crucial in sustainable travel. For shorter distances, trains and buses are significantly more eco-friendly than airplanes, emitting far less carbon per passenger. This choice reduces your environmental impact and often provides a more scenic and immersive travel experience.

If air travel is unavoidable, particularly for longer distances, look for airlines that offer carbon offset programs. These programs allow you to compensate for the emissions from your flight by funding environmental projects such as reforestation or renewable energy initiatives. By making these conscious choices in your mode of transportation, you play a direct role in reducing the carbon footprint of your travels, contributing to the broader effort of environmental conservation.

Insider’s Tip: Rent electric or hybrid vehicles for road trips to reduce your carbon footprint.

Support Local Businesses

Engaging with local economies is a key aspect of sustainable travel and a practice that directly benefits the communities you visit. By choosing locally-owned accommodations, dining at local restaurants, and selecting local tour operators, you’re not only immersing yourself in the authentic culture of the destination but also ensuring that your spending contributes directly to the local economy. This approach supports small businesses and helps to distribute tourism dollars more evenly, fostering community development.

Moreover, local establishments often have a smaller carbon footprint than larger international chains. They’re more likely to use local resources, employ residents, and preserve traditional practices. By making these choices, you help sustain the local culture and environment while reducing the overall emissions associated with your travel. This way, your journey becomes more meaningful, both for you and for the people whose home you’re visiting.

Insider’s Tip: Seek out accommodations that are known for their sustainable practices and community involvement.

Pack Light and Eco-Friendly

Packing light is an effective way to contribute to more sustainable travel. By reducing the weight of your luggage, you indirectly help lower the fuel consumption of flights, decreasing the carbon emissions associated with air travel. Lighter planes mean less fuel burned, making a small but meaningful environmental impact. Additionally, consider incorporating eco-friendly travel products into your packing list. Choose biodegradable toiletries that minimize your plastic waste and reduce the environmental impact of your personal care products. Carrying a reusable water bottle cuts down on single-use plastics and keeps you hydrated without adding to plastic pollution.

Furthermore, solar-powered chargers are a green alternative to traditional charging methods, harnessing renewable energy to keep your devices powered up. By making thoughtful choices in what and how you pack, you protect the environment while still enjoying the conveniences and necessities of modern travel.

Insider’s Tip: Choose a backpack or suitcase made from recycled materials for an extra sustainable choice.

Respect Wildlife and Natural Habitats

In natural settings where wildlife is present, it’s crucial to maintain a respectful distance. This ensures not only your safety but also the well-being of the animals. Interfering with wildlife can disrupt their natural behaviors and habitats. Avoid attractions or activities that exploit animals for entertainment, as these often contribute to animal stress and harm. Instead, opt for wildlife viewing experiences that promote conservation and ethical practices.

Additionally, when exploring natural areas, stay on marked trails. Straying off the path can destroy habitat and negatively impact the local flora and fauna. By sticking to designated trails, you help preserve the natural environment and ensure it remains a wildlife sanctuary. Your mindful actions contribute to the conservation of these ecosystems, allowing future generations to enjoy and appreciate the natural world just as you do.

Insider’s Tip: Choose wildlife tours led by reputable guides who prioritize animal welfare and conservation. Do not ride elephants!

Reduce, Reuse, Recycle

Adhering to the three Rs of sustainability – reduce, reuse, and recycle – is fundamental in minimizing your environmental impact during travel. Reducing waste starts with making conscious decisions about what you consume and how. Opt for products with minimal packaging, and whenever possible, choose alternatives to single-use plastics, like carrying a reusable water bottle, coffee cup, and shopping bags. Reusing items not only cuts down on waste but also saves resources. For instance, refill your water bottle, use the same shopping bag, and choose accommodations that offer bulk toiletry dispensers rather than single-use containers.

Recycling is the last step, but it’s equally important. Ensure you’re disposing of waste properly by separating recyclables from trash. Consider carrying recyclables in areas where recycling facilities might not be readily available until you find a proper disposal point. By following these practices, you help reduce the amount of waste that ends up in landfills or, worse, natural habitats and oceans, thereby playing a part in preserving the environment while traveling.

Insider’s Tip: Carry a ‘zero-waste kit’ with reusable cutlery, a shopping bag, and a coffee cup.

Conserve Water and Energy

Being conscious of water and energy usage is a crucial aspect of sustainable travel. Simple, everyday actions can collectively make a significant impact on conserving resources. Remember to turn off lights, air conditioning, and electronic devices when not in use or leaving your accommodation. This not only saves energy but also reduces unnecessary electricity consumption. Consider taking shorter showers, a practical way to reduce water usage, and reuse towels instead of requesting new ones daily.

Many hotels and accommodations now encourage this practice as part of their environmental policies. By being mindful of your water and energy consumption, you reduce your travels’ environmental footprint. These small but meaningful actions are steps towards more responsible and sustainable tourism, ensuring that the natural and cultural environments you visit can be preserved and enjoyed for years to come.

Insider’s Tip: Stay in accommodations that utilize renewable energy sources or have water-saving systems in place.

Educate Yourself and Others

As a responsible traveler, it’s important to educate yourself about the environmental challenges faced by the destinations you visit. This knowledge enhances your understanding of the local context. It enables you to make more informed decisions about how to travel responsibly. Awareness of these issues allows you to adjust your behavior accordingly, such as using water sparingly in drought-prone areas or avoiding products contributing to habitat loss, whether it’s water scarcity, pollution, or habitat destruction.

Furthermore, sharing your sustainable travel practices with fellow travelers is a powerful way to spread awareness and encourage others to adopt similar habits. Engaging in conversations about sustainability, sharing tips on eco-friendly practices, or even leading by example can inspire those around you to be more environmentally conscious. This collective effort can create a significant positive impact, helping to preserve the beauty and integrity of the places you visit.

Insider’s Tip: Participate in local environmental initiatives or workshops if available.

Offset Your Carbon Footprint

Considering the carbon emissions from your travel is an essential part of sustainable tourism. While traveling without leaving a carbon footprint is challenging, you can mitigate this impact by investing in carbon offsetting initiatives. These programs typically involve contributing to projects that reduce carbon emissions elsewhere, like renewable energy projects which replace fossil fuels, or reforestation efforts that naturally absorb carbon dioxide from the atmosphere.

When you choose to offset your emissions, you’re taking responsibility for the environmental impact of your travel. Many airlines offer carbon offset programs at the point of purchase. However, you can also independently invest in verified projects around the world. By offsetting your carbon emissions, you’re contributing to global efforts against climate change, ensuring that your travel positively impacts the environment.

Insider’s Tip: Use online carbon calculators to estimate travel emissions and find suitable offsetting projects.

Embrace Slow Travel

Embracing slow travel is about prioritizing quality over quantity in your journeys. Rather than rushing to tick off a long list of destinations, this approach encourages you to spend more time in fewer places. Doing so allows you to delve deeper into the local culture, gaining a richer and more authentic understanding of the places you visit. This immersive experience often leads to more meaningful connections with local people, traditions, and customs.

Additionally, slow travel significantly reduces the environmental impact associated with frequent travel, such as lower carbon emissions from less frequent flights or drives. This more relaxed pace of travel benefits the environment. It enhances your overall experience, allowing for a more thoughtful and fulfilling exploration of each destination.

Insider’s Tip: Choose a single destination or region and explore it thoroughly, using local transportation and enjoying off-the-beaten-path experiences.

Participate in Sustainable Activities

Engaging in low-impact activities is a key aspect of sustainable travel. Opting for experiences like hiking, biking, or kayaking allows you to enjoy and appreciate the natural beauty of your destination without contributing to pollution or resource depletion. These activities minimize your environmental footprint and provide a more intimate connection with nature. When selecting these experiences, consider those that offer educational insights into the local ecosystem or culture.

For example, guided nature walks can teach you about native wildlife and plant species, while cultural tours led by local experts can deepen your understanding of the area’s history and traditions. By choosing environmentally friendly and informative activities, you enrich your travel experience and support sustainable tourism practices that prioritize the health of our planet and its diverse ecosystems.

Insider’s Tip: Join guided eco-tours that focus on environmental education and conservation efforts. These tours provide insights into local sustainability practices and often contribute directly to conservation efforts.

Eat Locally Sourced Food

Eating locally sourced food while traveling is an opportunity to enjoy authentic flavors and dishes and an effective way to reduce your environmental impact. Food that is locally sourced hasn’t undergone long-distance transportation, which is a major contributor to carbon emissions. By opting for meals made with local ingredients, you reduce the demand for transported goods and your carbon footprint.

Furthermore, eating locally supports farmers and producers, contributing to the local economy and community. This approach allows you to experience the region’s culinary culture more intimately while supporting sustainable practices that benefit the environment and local livelihoods. It’s a simple yet impactful way to make your travel more environmentally friendly and culturally enriching.

Insider’s Tip: Visit local markets or farm-to-table restaurants to enjoy fresh, regional produce. This helps reduce transportation emissions associated with food and offers the chance to experience the region’s culinary culture more authentically.

Stay in Sustainable Accommodation

Choosing accommodations committed to sustainability is a significant step in responsible travel. Nowadays, many hotels and hostels are adopting eco-friendly practices, and by selecting these establishments, you’re actively supporting and encouraging the growth of green tourism. Look for places that utilize solar energy, which reduces reliance on fossil fuels, or those with effective water conservation measures, essential in areas facing water scarcity.

Recycling programs, use of eco-friendly materials, and efforts to reduce food waste are other green initiatives to consider. By opting to stay in such accommodations, you not only lessen your environmental impact but also help to drive demand for sustainable practices on the broader tourism industry. This consumer choice sends a strong message to the market about the importance of environmental responsibility, influencing more establishments to adopt similar practices.

Insider’s Tip: Look for eco-certifications or awards when booking accommodations, which often indicate a genuine commitment to environmental responsibility.

The Bottom Line

Sustainable travel is more than just being a responsible tourist; it’s about being a conscious global citizen and making choices that reduce our environmental impact while enhancing the well-being of local communities. By adopting these best practices, you become part of a growing movement that values environmental preservation, cultural respect, and the vitality of the communities and environments you visit.

This thoughtful approach to travel ensures that your experiences are enriching for you and beneficial for the planet. Choosing eco-friendly transportation, supporting local businesses, respecting natural habitats, and making mindful food and accommodation choices contribute to a healthier planet. Sustainable travel isn’t just about reducing harm; it’s about actively contributing to positive change, creating a ripple effect beyond your individual journey. 

As you explore the world, remember that every small action counts towards preserving the world’s beauty and diversity for future generations to explore and enjoy. Your choices can lead to meaningful experiences that align with sustainability principles, ensuring that the wonders remain for future generations to appreciate.

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Featured Image Credit: Shutterstock / Day2505.

For transparency, this content was partly developed with AI assistance and carefully curated by an experienced editor to be informative and ensure accuracy.

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Impact of COVID-19 Lockdown on Air Quality in Moscow

A. s. ginzburg.

1 A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, 119017 Moscow, Russia

V. A. Semenov

2 Institute of Geography, Russian Academy of Sciences, 119017 Moscow, Russia

E. G. Semutnikova

3 Department of Natural Resources Management and Environmental Protection of Moscow, 117198 Moscow, Russia

4 Moscow State University, 119991 Moscow, Russia

M. A. Aleshina

P. v. zakharova.

5 State Budgetary Environmental Institution Mosecomonitoring, 119019 Moscow, Russia

E. A. Lezina

The results of an analysis of changes in the atmospheric air quality in Moscow during the lockdown period and the decline in business activity caused by the COVID-19 coronavirus pandemic are presented. The observed changes in urban air pollution represent a unique experiment to assess the impact of various anthropogenic influences on the composition of atmospheric air. The influence of weather factors and transport activity on the level of pollution in the spring of 2020 is considered. The level of the main pollutants in the atmosphere decreased by 30–50% during the period of lockdown, and a different type of changes was revealed near highways and in residential areas. This article discusses the possibilities and difficulties of using a “unique experiment” on a sharp decrease in traffic intensity in large cities to determine the contribution of various branches of the urban economy (transport, energy, industry, waste processing) to the total air pollution in large cities.

INTRODUCTION

Natural and man-made disasters have a negative impact on the quality of life of mankind and the environment. Studying of these events creates new knowledge and technologies that can be used to prevent and mitigate the consequences of future disasters, improve the quality of life, and ensure the safety of the population.

Atmospheric air, water, and natural objects in large cities are most vulnerable to anthropogenic impact. The World Health Organization (WHO) estimates that diseases directly related to air pollution are responsible at present for 4.6 million deaths annually [ 1 ]. The anthropogenic impact is complex, since in urban agglomerations the climate, air quality, and the environment are simultaneously influenced by both global and regional natural factors (global warming, heat waves and cold snaps, etc.) and specific intra- and extra-urban factors (building, energy, industry, transport, landfills, etc.), the assessment of the relative importance of which is a difficult task (see for example [ 2 ]). In most large cities, it is difficult to distinguish the contribution of individual pollution sources, especially for various industrial enterprises and landfills, against the background of the main source of urban air pollution—transport. The atmospheric air composition in Moscow, the sources and concentrations of atmospheric pollutants, and trends in air quality in Moscow in comparison with the largest cities in the world are given in the reports of the Department of Natural Resources Management and Environmental Protection of Moscow (see, for example, [ 3 ]).

The COVID-19 pandemic has reduced by several times city traffic on the streets of Moscow and other cities in Russia and the world, accompanied by a noticeable economic recession and a decrease in industrial emissions that pollute the atmosphere of cities, as well as to a noticeable decrease in greenhouse gas emissions with possible climatic effects [ 4 ]. Ambient air quality monitoring data objectively demonstrate a significant reduction in the content of harmful substances. In many countries, especially in the densely populated areas of China and India [ 5 ], where aerosol air pollution is especially strong, since January of this year, there has been a sharp purification of air from suspended particles and engine emissions. Thus, the COVID-19 pandemic “set up a natural experiment” on the impact of a sharp decline in city traffic on urban air quality.

SOURCES OF AIR POLLUTION IN MOSCOW

The composition, concentration, and spatial–temporal distribution of the main air pollutants in Moscow are constantly monitored by automatic air pollution control stations (AAPCS network) of the State Budgetary Environmental Institution “Mosecomonitoring,” then annually summarized and analyzed in reports of the Department of Natural Resources Management and Environmental Protection of the Moscow Government. According to [ 3 ], within the boundaries of modern Moscow there are more than fifty AAPCSs located near highways, in residential, natural, and mixed territories. This paper analyzes the data of AAPCSs near highways and in residential areas ( Fig. 1 ).

Location of AAPCSs near highways and in residential areas within the boundaries of Moscow in 2011.

Due to the AAPCS network, the concentration of pollutants in the atmosphere of Moscow is quite well known. It is much more difficult to identify the main sources of Moscow air pollution. This is due to the fact that not all sources of air pollution in Moscow are located within the city’s administrative borders. At the same time, estimating emissions from various sources (transport, industry, waste) is a complex and difficult task, since the provision of data on emissions from various sectors of the urban economy is not always controlled by normative legal acts and is often a manifestation of the environmental responsibility of business. In addition, the transport and accumulation of pollutants in the city is highly dependent on specific meteorological conditions.

In Moscow, as in all large cities, the main source of pollutant emissions is motor transport, which creates a high spatial variability of pollution with a maximum near highways and a minimum in residential and suburban areas. The amount of vehicle emissions is a fully calculated value based on data on the emissions of different types of vehicles under different engine operating conditions.

The main contribution to emissions of pollutants by road transport in Moscow is made by carbon monoxide (almost 2/3 of all emissions); it is a product of incomplete combustion of fuel. The concentration of carbon monoxide depends on the configuration of the road network, traffic intensity, weather conditions, and street configuration. Its average concentration in recent years has been at the level of 0.36 mg/m 3 . Approximately 20% of transport emissions are nitrogen oxides, and slightly more than 10% are volatile hydrocarbons. Suspended particle emissions are about 1% excluding emissions from road surface abrasion and tires and brake pads of cars, which range from 2500 to 5000 tons/year [ 3 ].

CITY AIR DURING LOCKDOWN

Reductions in air pollution during the COVID-19 restrictions have been observed in many cities and regions of the world (see, for example, [ 4 – 7 ] and other publications in spring and summer 2020). Most of these publications are based on satellite observations of atmospheric gases (mainly nitrogen dioxide). Ground-based measurements of the dynamics of atmospheric pollution during lockdown have not yet been analyzed sufficiently. Only a few publications can be noted, for example [ 7 ], where the aerosol content was compared before and during lockdown in Almaty according to data from one station in the city center.

In Moscow, from early April to mid-May 2020, mainly reduced concentrations of pollutants were observed. This could have been due to the significant decrease in the traffic intensity of vehicles, emissions from which in a normal situation make up more than 90% of the total emissions of pollutants into the atmosphere of Moscow. According to the Moscow Department of Transportation, the Moscow motorway network workload in April 2020 was approximately four times less than in April 2019 [ 8 ].

The average concentrations of pollutants in April 2020 were lower than the average for the previous three years. At the same time, the decrease in air pollution manifests itself in different ways near highways and in residential areas ( Table 1 ).

Decrease in the average concentration of the main pollutants in the atmospheric air of Moscow in April 2020 compared to the average level in recent years (in percent) according to the data of the State Budgetary Environmental Institution “Mosecomonitoring”

Table 1 shows an interesting fact that characterizes the transport and deposition of pollutants in the city’s atmosphere and which shows that during the quarantine and the corresponding restriction of transport activity, the air inside residential areas was purified stronger than near highways.

It should be noted that it is particularly difficult to assess the impact of lockdown on air quality in Moscow in the second quarter of 2020. First, in the spring, after snow melt, an increase in the content of atmosphere pollutants and especially suspended particles usually happens in the Moscow Region. In 2020, there was an extremely snowless winter, as a result of which the seasonal trend of aerosol content in the Moscow air in the first half of the year could have been atypical. Second, at the end of March 2020, there was a period of a positive pressure anomaly, which led to a strong development of unfavorable meteorological conditions that contributed to the accumulation and a multiple increase in the content of pollutants in the surface layer of the atmosphere. This was followed by a decrease in pressure in April and the first half of May. Thus, the pressure trends from March to May were generally similar to the dynamics of the transport activity index in Moscow. Due to the meteorological features of spring 2020, in order to identify the causes of air quality changes during lockdown relative to the average data obtained by the State Budgetary Environmental Institution “Mosecomonitoring” for the period 2017–2019, a thorough analysis is required.

Changes in the average daily concentrations of pollutants in Moscow in March–May 2020 relative to the average values for 2017–2019 are shown in Fig. 2 . The sea level air pressure values are also shown. A sharp short-term jump in concentrations for March 27–28, as mentioned above, is associated with a powerful positive pressure anomaly and unfavorable conditions for dispersion of impurities. Despite the meteorological features of the spring of 2020, one can note the dependence of the content of a number of pollutants and, first of all, carbon monoxide on the decrease in transport activity in Moscow (transport activity was estimated according to the data of the Moscow Department of Transport [ 8 ]).

Change in (a) CO and (b) PM 10 concentrations in the spring of 2020 compared to the average values of 2017–2019 (in %) for AAPCSs near highways (red lines) and in residential areas (green lines). The purple line shows the atmospheric pressure at sea level according to the Balchug weather station (in hPa).

During the quarantine period, the Moscow Department of Transport promptly published data on the intensity of passenger traffic in public and private transport in the city. Since the passenger traffic of public transport is measured in millions of people transported per day, the data on personal transport flows were given in the same units. Data on public transport passenger flows are not very informative for the purposes of this study, since this transport includes not only buses, the emissions of which pollute the urban atmosphere, but also electrified transport—subway, electric trains, trams, and trolleybuses. Due to the predominant number of personal vehicles in the total number of cars on the roads of Moscow (according to Mosgortrans and the Traffic Management Center (TMC), the number of passenger cars exceeds the number of buses by more than 100 times) and the proportionality of the number of passengers to the number of cars, data on passenger traffic in terms of personal transport can be used as an index of general transport activity in the city.

In March 2020, before the lockdown, the CO content near highways significantly exceeded its content in the air of residential areas. In April and early May, the CO content in the city as a whole decreased significantly, while its concentrations near highways and in residential areas became closer to each other. Since the middle of May, as the restrictions were removed and transport activity increased, the CO concentration began to grow, and it increased near highways much faster than in residential areas ( Fig. 3 ).

CO concentrations trend in spring 2020 for stations near highways (red lines) and in residential areas (green lines). The dynamics of personal transport passenger traffic (million people/day) is shown in gray.

The importance of taking into account weather conditions for the interpretation of air purification in cities during quarantine has also been noted by American scientists [ 9 ]. According to them, the noticeable decrease in nitrogen dioxide (NO 2 ) content observed from satellite data in March–April 2020 in different cities of the United States depends significantly on the precipitation regime in the corresponding regions of the country. Similar conclusions were obtained for pollution in Chinese cities, where extremely high levels of pollution associated with weather conditions were observed against the background of a general decrease in the level during lockdown [ 5 ].

DISCUSSION AND CONCLUSIONS

An analysis of the improvement in air quality in Moscow during the restrictions imposed by COVID-19 showed a difference in the impact of a decrease in economic activity on the content of various atmospheric pollutants near highways and in residential areas of the city.

At the same time, difficulties were found in accounting for weather conditions for interpreting urban air purification during lockdown and comparing observations in the spring seasons of various years.

Further analysis of changes in the content of atmospheric pollutants in the context of a sharp decline in economic activity will help to improve methods for assessing the contribution of various sources to air pollution and the impact of reduced traffic on air quality.

For reliable quantitative assessments of the effect of reducing traffic and reducing economic activity on the content of pollutants in the urban atmosphere, it is necessary to take an inventory of the composition and amount of emissions of gas and aerosol pollutants into the atmosphere from various types of industrial enterprises, energy facilities, trade (including public catering facilities), everyday services, and other urban sectors, as well as landfills and waste processing enterprises, taking into account the specifics of various cities in Russia, such as Moscow, St. Petersburg, Omsk, and Chelyabinsk, where the ratio of emission sources is different and at the same time there is a sufficiently developed observation network.

The results of such a study can be used for planning the “green” development of the urban economy and environmental “improvement” of industrial enterprises.

This work was supported by the Russian Science Foundation, project no. 19-17-00242, and the Russian Foundation for Basic Research, project no. 20–05–00254.

Translated by V. Selikhanovich

Environmental Pollution in the Moscow Region According to Long-term Roshydromet Monitoring Data

• Published: 02 November 2020
• Volume 45 , pages 523–532, ( 2020 )

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• G. M. Chernogaeva 1 , 2 ,
• L. R. Zhuravleva 1 ,
• Yu. A. Malevanov 1 ,
• N. A. Fursov 3 ,
• G. V. Pleshakova 3 &
• T. B. Trifilenkova 3  

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Long-term Roshydromet monitoring data (2009–2018) on the pollution of the atmosphere, soil, and surface water are considered for the Moscow region (Moscow city within its new boundaries and the Moscow oblast). The air quality in the megacity (Moscow) and in background conditions (Prioksko-Terrasny Reserve) is compared.

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Izrael Institute of Global Climate and Ecology, 107258, Moscow, Russia

G. M. Chernogaeva, L. R. Zhuravleva & Yu. A. Malevanov

Institute of Geography, Russian Academy of Sciences, 119017, Moscow, Russia

G. M. Chernogaeva

Central Administration for Hydrometeorology and Environmental Monitoring, 127055, Moscow, Russia

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Russian Text ©The Author(s), 2020, published in Meteorologiya i Gidrologiya, 2020, No. 8, pp. 9-21.

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Chernogaeva, G.M., Zhuravleva, L.R., Malevanov, Y.A. et al. Environmental Pollution in the Moscow Region According to Long-term Roshydromet Monitoring Data . Russ. Meteorol. Hydrol. 45 , 523–532 (2020). https://doi.org/10.3103/S1068373920080014

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Received : 06 February 2020

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Accepted : 06 February 2020

Published : 02 November 2020

Issue Date : August 2020

DOI : https://doi.org/10.3103/S1068373920080014

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'Things have started to improve': Moscow residents share thoughts on the city's changes

From cycling infrastructure to public spaces, how do Moscow’s residents feel about the city’s urban renewal projects? Here they share their stories

The ‘Moscow experiment’ has seen the city undergo renewal efforts over the last five years to improve liveability. But what do Moscow’s residents really think about the changes? We asked you to share your stories of life in the Russian capital, and reflect on whether Moscow is changing for better or worse.

The city centre may be seeing improvements in infrastructure and public space, but what about the suburbs? How involved have local citizens been in the changes? And what does the future hold for Moscow? We’ve rounded up a selection of your GuardianWitness contributions , comments and emails, which reveal the everyday experiences of Moscow’s transformations:

About pedestrians and automobilists

Moscow has undergone massive change in the last five years, but the most obvious developments concern parks, streets, and general navigation in the capital. Most of the developments are surely positive: the city has seemed to get more air. There have appeared more walking paths, pedestrian zones have been expanded, some streets have been closed for traffic altogether, parks are being renovated, and new bicycle lanes are being offered now to city residents and its guests. However, there are negative changes as well, which have largely affected car owners: extension of the paid parking areas, and the increase of the average price, the need to navigate a bypass route in order to drive round pedestrian zones. But this coin has another side too: fewer cars in the centre means less exhaust fumes and cleaner air. Muscovites look forward to the old parks being renovated, and the new ones being opened. New plans make excited everyone: new metro stations, new roads, new bicycle lanes and pedestrian footpaths.

It's changing for better

Moscow is definitely changing for better now. As I see it, the authorities are trying to make a city a better place to live in, especially in remote residential neighborhoods, which is very good. Many parks were renovated, cycle lanes appeared. Moscow has become a nice place for long walks and cycling. The city has a lot to offer now including museums, and different events like exhibitons, summer outside activities and others. It's a pity that it takes so long but taking into account the size of the city and its population I can say the situation has changed even if compared to what it was like 4-6 years ago.

I grew up in Moscow and lived here until two years ago. My general impression is that the people making the decisions are trying to copy some European practices like bike rental, parks, etc, but the general success is limited. The streets still belong to drivers, not to pedestrians, to an unbelievable extent. Another thing is that street retail was banned in an attempt to improve the city. It works for the city centre, where retailers really spoiled the overall impression of the scene, but 80% of Moscow is not a city centre. And there, this removal makes your life more difficult. The positive trend is all these multiple festivals, exhibitions, etc, but the best of all these events were initiated by citizens, so I would say that it is due to improving integration of Muscovites into the global world. Overall, I should admit that I love my homeland, but there is still a far way to go to make the city as comfortable as it could be, and the incentives of the people in charge in many cases do not have a lot to do with the wellbeing of Muscovites. - Ekaterina Ivanova

In the city

Gorky central park of culture and leisure

Better, definitely.

I was born in Moscow, emigrated to the UK ten years ago, and have been coming back at least once a year ever since. Although it's hard to tell from only a short visit, I can definitely see improvement in the capital: public transport operates better, local government services are better organised, the streets are cleaner... in my old neighbourhood (a very working-class, high-immigrant community), there are more 'high-street' shops appearing, less potholes on the roads, new playgrounds, new trees being planted and even the occasional fountain being built. These things may seem little and shallow, but I can certainly see improvement in this sense, at least.

It’s better on the surface, but still has inclusion and institutional issues. What do I mean? I mean that no one really asked us, Moscow residents, about the changes being made in the city (although we really welcome a big part of them). And lack of inclusion and mutual trust between the residents is in the end the main problem of Moscow as a city and a community (in my opinion). You can build as much fancy stuff as the money allows you to but if the Muscovites do not trust each other and don’t consider this city to truly belong to them, it will never become a real city and will continue to exist as “a big village” with fancy parks, craft beer and bicycle service. - Sergey Kurakov

When you smiling

Moscow is beautiful with the history, but it's even more beautiful when history meets modern cultural programmes. This installation is a part of one of them. Such things can be seen in the city when we have holidays

The transformation of Gorky park was nice but it is now overly popular which means it is not so pleasant to go to. The boulevard ring has in the main been transformed and makes for a pleasant walk. The banks of the Moskva have been transformed and the walk from Red October down to Gorky park is now interesting, however I always feel that Moscow does not make as much as it's river as other cities (Paris or London for example) do. The area around modern tretyakov could be transformed into an area more like the south bank.

However the biggest killer of Moscow life are simply the size of the roads. They are everywhere and take priority over pedestrians. To really improve Moscow life would be deal with the massive structural change required for dealing with traffic. And that, unfortunately, costs more than plants.

I was born in Moscow and truly love it. And this city inspired me to take an urban planning course: I honestly just couldn’t figure out how one of the wealthiest cities in the whole world could experience such a plethora of problems ranging from car invasion to banal low visual and urban design culture. Many things have changed for the better. A lot of new creative things emerged, such as anti-cafes, high-quality bars and famous Moscow art-clusters. These all influence the city and make it somewhat more democratic. On top of that, there are more direct influences on its physical fabric due to new urban design studios like StrelkaKB, Wowhaus and many others. However, the overall system is still underdeveloped. Moscow is not really clean, it is over-reliant on cars and it seems not much action is taken to improve that; it’s incredibly unfriendly to wheelchairs and people of similar mobility. We still get enormous unnecessary shopping malls planted close to the centre. Moscow is a wonderful city and sure enough it is gradually developing, however, only in a discrete, tactical way, largely and mostly driven by private interests. The public sector, in turn, seems to provide no clear strategic policy to turn Moscow in a healthy modern democratic city with all its problems tackled in one way or another. - dmitryBooM

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