In the grand scheme of things, aviation may not represent a huge source of concern with respect to climate change. But neither should the aviation industry (airports included) ignore the fact that aviation does contribute to climate change not only through the emission of carbon dioxide (CO2) but also through the emission of nitrogen oxides (NOx), aerosols and their precursors (soot and sulfate), and increased cloudiness in the form of persistent linear contrails and induced-cirrus cloudiness. The intent of this series of articles is to examine the effect aviation has on climate change, outline the regulatory and legal framework that is developing, and to suggest avenues for the aviation industry to pursue in the future. The first challenge is to clear up some misconceptions about aviation and climate change so that we can move forward with accurate and up-to-date information.
II. Some Facts About Aviation and Climate Change
In Aviation and Climate Change: the Views of Aviation Industry Stakeholders, the aviation industry makes several claims regarding the impact aviation has on climate change. First, the industry claims that “over the past four decades, we have improved aircraft fuel efficiency by over 70 percent, resulting in tremendous savings.” As a result, the industry continues, “given the significance of fuel costs to the economic viability of our industry, our economic and environmental goals converge.” Second, the industry claims that “because of our aggressive pursuit of greater fuel efficiency, greenhouse gas (GHG) emissions from aviation constitute only a very small part of total U.S. GHGs, less than 3 percent.” However, in order to assist the industry in its obligation “to further limit aviation’s greenhouse gas footprint even as aviation grows to meet rising demand for transportation around the world,” those claims of progress need to come under a microscope.
A. Contribution of Aviation to Climate Change Remains Subject to Debate
First, how much aviation contributes to climate change is still up to debate. Several governmental and aviation industry organizations have been reporting a “less than 3%” number for quite some time while environmental groups, particularly in Europe, claim that the percentage is anywhere from 5 to 9%. In examining the claims and counterclaims concerning emissions of GHG, one has to be very careful about the language and the metrics used in determining the “impact” any given industry will have on “climate change.” Many reports and studies focus only on CO2, since the amount of CO2 produced both naturally and by humans is overwhelming. However, as just about everyone knows by now, there are other gases and anthropogenic actions that exacerbate climate change. For example, the U.S. EPA recently proposed regulations that would require major emitters of six “greenhouse gases” to report their emissions to the EPA on an annual basis. Those six greenhouse gases are: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), perfluorochemicals (PFCs), and other fluorinated 20 gases (e.g., nitrogen trifluoride and hydrofluorinated ethers (HFEs)). It also should be kept in mind when discussing climate change, especially with respect to aviation, that water vapor is estimate contribute anywhere from 36% to 72% of the greenhouse effect. This is important because the radiative forcing effect of cirrus cloud formation from the aircraft is a significant contributor to the greenhouse effect. As pointed out above, it is generally accepted that for aviation the GHGs of concern are CO2, nitrogen oxides (NOx), aerosols and their precursors (soot and sulfate), and increased cloudiness in the form of persistent linear contrails and induced-cirrus cloudiness.