I've long suspected that exhaust from airplanes, by virtue of being released high in the atmosphere, is more problematic than exhaust from cars and trucks. A new study in the prestigious journal Nature confirms that air travel causes more climate disruption, but not for the reason I imagined.
It turns out that condensation trails, or contrails, trigger formation of cirrus clouds much like those which form naturally. Cirrus clouds are high, thin and wispy, and they appear when moist air meets temperatures cold enough for ice formation. These clouds trap heat in the atmosphere, and the authors estimate that short-term warming from contrails is about equal to long-term warming from the plane's release of carbon dioxide. The climate footprint of air travel, therefore, is double what you'd calculate looking only at fuel consumption.
More study is needed to fully understand the climate impacts of jets, but it's safe to say that we need to view air travel as a luxury, not a convenience. In a gluttonous age, routine air travel may be our biggest indulgence.