Luftverkehr und Klima

Carbon dioxide emissions from past global air traffic contributed nearly 2% to the increase of this greenhouse gas during the last century. For continued trends, this fractional contribution may increase up to 5% within the next 50 years. Nitrogen dioxides emitted from presently operating aircraft engines approximately doubled the concentration of this gas in the Northern mid-latitude upper troposphere, i.e. at altitudes between 8 and 12 km. The nitrogen oxides emissions presently increase the ozone concentration by a few percent in that region. The increase in ozone is too small to be detectable from existing measurements. There is no evidence for ozone depletion by aircraft emissions in the stratosphere. The radiative forcing due to additional ozone has been computed to be of the same order as the radiative forcing caused by past carbon dioxide emissions from aircraft. Whereas the ozone effect is a function of the actual rate of emissions, the carbon dioxide effect depends for many decades on the integral of the emissions in the respective past period. Therefore, the fraction of radiative forcing by aviation caused by carbon dioxide emissions is increasing. The importance of contrails, soot, sulphuric acid and other particles, and related changes in cloudiness cannot yet be fully assessed. The impact of global air traffic on global climate is larger than its share in global emissions but still small compared to natural climate variations. A reduction of present flight altitude or speed does not reduce the climate impact. Engines with less nitrogen oxides emissions and a more fuel-efficient aviation system should be developed and installed. Much additional insight has been gained during recent years on the impact of aviation on the global atmosphere and has been reviewed by the Intergovernmental Panel on Climate Change (IPCC 1999). The reader should refer to that report for more details