Impact of present aircraft NOx and aerosol emissions on atmospheric composition and climate: results from a model intercomparison

Kurzfassung

This study presents results from a new model intercomparison of the impact of aircraft emissions involving five state-of-the-art global models including both tropospheric and stratospheric chemistry. Aircraft NOx increases ozone photochemical production in the free troposphere throughout the year and decreases ozone chemical loss in the high-latitude lowermost stratosphere during spring–early summer. The models generally agree on the spatial pattern of NOx, ozone, and hydroxyl radical (OH) responses. The NOx net ERF is systematically positive with a model mean of 18.3 mW m−2, ranging from 9.4 to 24.5 mW m−2 among the different models. This net NOx forcing is reduced by 35 % and 43 % accounting for the negative forcing arising from the formation of nitrate and sulfate particles, respectively. Estimates of the aerosol direct ERF are systematically negative and range between −6.5 and −17.8 mW m−2, compensating most of the net NOx ERF albeit with noticeable intermodel differences arising from the diversity in aerosol parameterizations.