Air Travel and Climate Change

How much do greenhouse gas emissions from aircraft contribute to climate change?

Although aviation is a relatively small industry, it has a disproportionately large impact on the climate system. It presently accounts for 4-9% of the total climate change impact of human activity.

But at a time when we urgently need to reduce our greenhouse gas emissions, emissions from aviation continue to grow. For example, since 1990, CO2 emissions from international aviation have increased 83%. The aviation industry is expanding rapidly in part due to regulatory and taxing policies that do not reflect the true environmental costs of flying. ‘Cheap’ fares may turn out to be costly in terms of climate change.

Compared to other modes of transport, such as driving or taking the train, travelling by air has a greater climate impact per passenger kilometer, even over longer distances (see graph below). It’s also the mode of freight transport that produces the most emissions.

CLICK HERE FOR LARGE IMAGE
^{CO2 intensity of passenger transport. Note that if the upper atmosphere impacts of air travel were included, emissions from air travel would be 2.7 times greater than shown in this diagram.}

What sorts of greenhouse gases do aircraft produce?

When jet fuel is burned, the carbon in the fuel is released and bonds with oxygen (O2) in the air to form carbon dioxide (CO2). Burning jet fuel also releases water vapour, nitrous oxides, sulphate, and soot. Aircraft emissions trigger the formation of contrails (condensation trails), and contribute to the formation of cirrus clouds.

A special characteristic of aircraft emissions is that most of them are produced at cruising altitudes high in the atmosphere. Scientific studies have shown that these high-altitude emissions have a more harmful climate impact because they trigger a series of chemical reactions and atmospheric effects that have a net warming effect. The IPCC, for example, has estimated that the climate impact of aircraft is two to four times greater than the effect of their carbon dioxide emissions alone.

What are "contrails" and what is their impact on climate change?

Contrails are the long plumes of exhaust that can be seen in the sky behind airplanes. They consist primarily of water droplets and ice, and are formed when water vapour released from burning jet fuel condenses at higher altitudes. Contrails may stay in the sky for many hours, and can spread 2 kilometres wide before dispersing. The net effect of these contrails is to trap heat that would otherwise escape from the earth, which contributes to global warming. Studies have shown that night flights have the strongest warming impact, because during the daytime contrails actually reflect some sunlight away from the earth.

What’s being done about emissions from air transportation?

Not much, unfortunately. Countries with national emissions targets under the Kyoto Protocol, like Canada, are only required to account for emissions from domestic flights. Emissions from international flights are not counted. And very little has been done to actually limit these emissions. To date the only formal plan to control and reduce international aviation emissions is being developed within the European Union (EU).

Is it likely that new technologies or fuels will make air transportation more efficient in the near future and help reduce its climate impact?

Right now there is no climate-friendly alternative to the kerosene fuel burned by airplanes, and there is no indication that solar or hydrogen-powered aircraft can be expected anytime soon. In terms of efficiency, it appears that improvements in current aircraft technology have nearly reached their limit, and further significant fuel efficiency gains will only come from the development of radically new airplane designs and systems. The time, cost and coordinated effort it would take to develop and test such designs, and then phase them into the world’s fleets of aircraft, make this unlikely to happen anytime soon, and an impractical solution for the urgent problem of climate change. In reality, the small, incremental gains that we can reasonably expect in aircraft fuel efficiency will be eclipsed by the projected growth in the industry.

What can I do?

Because the climate impacts of air transportation are at present not adequately regulated under national or international laws, the onus is on individuals and businesses to limit their flying unless absolutely necessary. This needn’t be as drastic as it sounds:

• Consider taking a vacation closer to home. You’ll save money and avoid the stress of airport security, travelling to and from the airport, and sitting in those tiny seats. Most of us live in places that tourists from elsewhere visit, so take a holiday in your hometown or region and find out what it has to offer.

• Use other modes of transport where possible. Trains and buses, for example, are much more energy efficient than airplanes, and for regional trips can even be faster when airports are factored in. Even cars can be more efficient than planes --especially with more than one passenger.

• Use video-conferences for meetings. Companies like Swiss Re and IKEA are using video-conferencing to reduce business air travel. Companies benefit from reduced costs, and more efficient decision-making about travel. Employees avoid the stress of travelling and time away from home and family.

• Use webcams to keep in touch with family and friends who live far away.

• Contact your political representatives, tell them you’re concerned about the contribution of aviation to global climate change, and ask them to take action to regulate and limit greenhouse gas emissions from this sector.

If you do have to fly:

• Try to minimize the number of flights you take by combining trips. For example, book more than one meeting in your destination city, so you don't need to fly there several times.
  
  
• Fly during the daytime, because studies have shown that flights taken at night have a greater impact on the climate.
  
  
• Fly economy, because more people per plane means fewer emissions per person.
  

• Pack light, because lighter planes mean less fuel is burned.                      
  
  
• Purchase carbon offsets to account for the emissions from your flight. See our carbon neutral webpage for more information. If the airline or travel agent you are using doesn't currently offer its customers the option of offsetting their flights, ask them to consider it.
  

What is the David Suzuki Foundation doing?

In Fall 2006 the David Suzuki Foundation purchased videoconferencing equipment for its Vancouver office. We already rely on phone conferences for many of our meetings, and look for ways to minimize travel to conferences, training sessions and other functions. We currently purchase high quality carbon offsets for all Foundation air travel. We are also taking an office-wide look at our air travel requirements, seeking further reduction opportunities.

Further Information

Clearing the Air – The Myth and Reality of Aviation and Climate Change

The Sky’s the Limit – Economist article

Toolkit for Reducing Business Air Travel

Flying Green: How To Protect the Climate and Travel Responsibly  - Tufts University

Night Flights Give Bigger Boost to Global Warming - New Scientist

Aviation and the Global Atmosphere - IPCC

Predict and Decide: Aviation, Climate Change and UK Policy

Aviation Growth 'Risk to Planet' - BBC