Blue Skies and Greenhouse Gases: Is Air Travel Really a Big Deal?

October 24, 2007

When considering the impact of transportation on the environment, most people think of cars. However, air travel is gaining increasing scrutiny as a climate change culprit. Are people and organizations in your region aware of how their flying habits affect global climate? How significant is this impact? And what, if anything, are today's air travelers willing to do about it?

In June 2006, reported that "Air travel accounts for about 3.5 percent of the human contribution to global warming," according to the Intergovernmental Panel on Climate Change (IPCC).

At issue is not just today's air travel, but tomorrow's. IPCC says "CO2 emissions from aircraft in 1990 account for about 2.4% of the total; they are projected to grow to about 3% or more than 7% of all fossil fuel carbon emissions by 2050".


Air travel is now more popular than any time since 9/11. In March 2007, the Official Airline Guide (OAG, an air travel industry research and publishing organization) reported that the number of flights scheduled in October 2007 is 3% higher than in the same month last year. ...the highest October figure for more than five years."

Federal statistics also indicate the increasing popularity of air travel. On Oct. 15, 2007, the US Dept. of Transportation's Bureau of Transportation Statistics (BTS) reported: "US. airlines carried 72.2 million scheduled domestic and international passengers on their systems in July, a record high for a single month and 2.2 percent more than the previous record of 70.6 million in July 2005." BTS press: Dave Smallen, 202-366-5568; release.

That said, air travel is still far from the most popular choice for long-distance travel. According to the most recent (2001) BTS data, 90% of long-distance trips are by personal vehicle, and only 7% are by air. However, nearly 75% of long-distance round trips over 2,000 miles were made by airplane.

US EPA data indicate that the air travel business (commercial and military) might be reining in its emissions: "In contrast to other transportation sources, aircraft saw only a modest (4%) increase in GHG emissions between 1990 and 2005, despite a substantial rise in passenger miles traveled. The small increase reflected a large decline in emissions from military aircraft (50%) and a 16% increase in emissions from commercial aircraft. Greenhouse gas emissions from commercial aircraft rose 21% between 1990 and 2000, but then declined in 2001, 2002 and 2003, due largely to a decrease in air travel following the September 11, 2001 terrorist attacks."


Mainly from burning jet fuel and emitting carbon dioxide.

But air travel also disturbs the chemistry and physics of the upper atmosphere in other ways. According to the IPCC, "Aircraft ...change background levels of trace gases and particles and by forming condensation trails (contrails). Aircraft emissions include greenhouse gases such as CO2 and H2O that trap terrestrial radiation and chemically active gases that alter natural greenhouse gases, such as O3 and CH4. Particles may directly interact with the Earth's radiation balance or influence the formation and radiative properties of clouds. ...A causal chain whereby the direct emissions of aircraft accumulate in the atmosphere, change the chemistry and the microphysics, and alter radiatively active substances in the atmosphere, which change radiative forcing and hence the climate".

And of course, commercial and military air travel operations involve more than just airplanes. When you factor into air travel's carbon footprint emissions from energy use at airports and other plane-related facilities; air freight (especially overnight delivery services); vehicles for ground support and maintenance; and the energy required to manufacture, transport, and store jet fuel, the picture can change substantially.

More context from the Federal Aviation Administration:


To a large extent, this is a business story. In recent years jet fuel costs have been rising sharply, giving airlines and airplane manufacturers considerable motivation to improve fuel efficiency. For most commercial airlines, fuel comprises up to 30% of total operating costs - a threefold growth in five years, according to industry analyst Jeff Siegel.

The main strategies to cut CO2 emissions from air travel are:

  1. Improve airplane fuel efficiency (more efficient engines, reduced aircraft weight or wind resistance).
    • On Sept. 28, 2007, the International Civil Aviation Organization created a new group on international aviation and climate change to work out a framework for reducing the industry's greenhouse gasemissions (release). Also, the industry magazineAviation Week covers technological developments in detail for commercial, military, and other aviation sectors. Search the site for "fuel efficiency" or "climate change" to find lots of stories.
    • The Air Transport Association of America claims that since 2000 alone its member carriers have increased fuel efficiency by 23%. ATA Press: David A. Castelveter, 202-626-4033.
  2. Streamline air traffic patterns and control. On June 18, 2007, AP reported an agreement between the US and EU to cut emissions from aircraft by improving air traffic control systems.
    • The FAA also has an "airspace redesign" program for the congested NY/NJ/Philadelphia region.
    • FAA press: Arlene Salac-Murray or Jim Peters, 718-553-3015.
  3. Cap-and-trade systems regulating air travel CO2 emissions. The EU is pushing for this, but the current US administration opposes such a system.
  4. Reducing fuel consumed per passenger (generally, cramming more people into each flight).
  5. Reducing the amounts of travelers, trips, or freight handled via air. (Ideally eliminating unnecessary air transport, or shifting it to transport options that would produce less overall greenhouse gases.)

    Telecommuting and virtual meetings are increasingly touted as environmentally-friendly alternatives to business travel, including air travel. One example of this is WebEx.

  6. Participating in carbon offset programs to "neutralize" the impact. This angle is popular in airline marketing - but as noted in the Apr. 25, 2007, TipSheet, carbon offset programs warrant careful scrutiny.

What are the airlines doing to cut emissions? Due to rising fuel costs, every airline is trying to improve fuel efficiency and also trying to spin that as green marketing. You can learn about individual airlines' efforts under the environment section of their web sites. Check the "Airline" section of Business Travel News online for relevant breaking news and analysis.


The logical place to start is to get familiar with air travel trends for the closest major airport. BTS offers a variety of statistics on most major US airports. Generally, departure-related figures are more relevant to the travel habits of area residents and businesses.

What are the most popular routes departing from your local airport, and what kinds of planes tend to be used on those routes?

  • ChooseClimate offers a flight carbon footprint calculator (based on IPCC-TAR formulae) that allows you to calculate the likely CO2 emissions for those flights. ChooseClimate creator: Dr. Ben Matthews, Georges Lemaitre Institute of Astronomy and Geophysics, Universit Catholique de Louvain, Belgium.

Many carbon footprint calculators are available online, each with unique assumptions and varying levels of relevance to a community's data needs. If you're writing about climate change and what local people or organizations can do to gauge or minimize their carbon footprint, be sure to recommend carbon footprint calculators that ask about air travel. Here's one example.

A fun story can be profiling the carbon footprint of local individuals or businesses with and without air travel factored in. If there are a lot of self-employed consultants, frequent business travelers, migrating students, or people working for "virtual companies" in your area, the contribution of air travel to their carbon footprint can be quite striking.

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