AirClim: an efficient tool for climate evaluation of aircraft technology
Climate change is a challenge to society and to cope with requires assessment tools which are suitable to evaluate new technology options with respect to their im-pact on global climate. Here we present AirClim, a model which comprises a linearisation of atmospheric processes from the emission to radiative forcing, resulting in an esti-mate in near surface temperature change, which is presumed to be a reasonable indicator for climate change. The model is designed to be applicable to aircraft technology, i.e. the climate agents CO 2 , H 2 O, CH 4 and O 3 (latter two resulting from NO x -emissions) and contrails are taken into account. AirClim combines a number of precalculated atmospheric data with aircraft emission data to obtain the temporal evolu-tion of atmospheric concentration changes, radiative forcing and temperature changes. These precalculated data are de-rived from 25 steady-state simulations for the year 2050 with the climate-chemistry model E39/C, prescribing normalised emissions of nitrogen oxides and water vapour at various at-mospheric regions. The results show that strongest climate impacts (year 2100) from ozone changes occur for emis-sions in the tropical upper troposphere (60 mW/m 2 ; 80 mK for 1 TgN/year emitted) and from methane changes from emissions in the middle tropical troposphere (−2.7% change in methane lifetime; –30 mK per TgN/year). For short-lived species (e.g. ozone, water vapour, methane) individ-ual perturbation lifetimes are derived depending on the re-gion of emission. A comparison of this linearisation ap-proach with results from a comprehensive climate-chemistry model shows reasonable agreement with respect to concen-tration changes, radiative forcing, and temperature changes. For example, the total impact of a supersonic fleet on radia-tive forcing (mainly water vapour) is reproduced within 10%. A wide range of application is demonstrated.