Nitrogen Oxide Emissions from Air Traffic

About 153 million metric tons of aviation fuel were consumed in 1987, which was ca. 13% of the world's consumption of transportation fuel. Burning this fuel produced ca. 2.75 million tons of nitrogen oxides, calculated as NO2, using an average emission index EI of 18 g NO2 per kg fuel. 0.92 million tons of NO2 was exhausted between 9 and 13 km, which is an especially endangered altitude range, estimated with an EI of 15 g NO2 per kg fuel. Air traffic is the main NOx source between 9 and 13 km. Since the NOx background concentration at this altitude is low and the possible lifetime of an admixture two orders of magnitude larger compared to the ground, these NOx emissions can lead to an important increase of tropospheric ozone, which contributes to the global greenhouse warming. Alternatively, NOx emitted in the lower stratosphere may contribute to stratospheric ozone depletion, especially at high latitudes