From: felton@phoenix.Princeton.EDU (phil. Felton) Organization: Princeton Univ. Date: 25 May 96 14:40:21 References: 1 2 3 Followups: 1 2
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In article <airliners.1996.778@ohare.Chicago.COM>, C++ Freak <firstname.lastname@example.org> wrote: > Of course, figures from Deutsche Airbus show a low environmental impact > of air traffic. > It is not the greatest: automobile traffic and fossil power plants are the > worst, but according to other figures is is currently 2 % of the CO2 output > which still seems low but still of concern because of: > - increasing *rapidly* because air travel is getting cheaper and governments > strongly subsidize airlines and airports > - it affects the upper atmosphere which other polluters don't. And the state of > the upper atmosphere probably affects the climate more than the lower > atmosphere. This is incorrect, the altitudes that are flown by commercial airlines are <40000 feet. The atmosphere up to the tropopause is well mixed and therefore the altitude of emission is irrelevant, SSTs on the other hand fly higher and NOx emissions there are of more concern. However, note that the main source of NOx in the stratosphere is from agricultural fertilizers! To illustrate the degree of mixedness note that Mauna Loa where the classical set of data on CO2 is taken (at an altitude of about 13,000 ft) shows a ~2% annual fluctuation due to the seasonal growth and die back of vegetation. Phil.