The global climate is changing. According to IPCC a large fraction of this change is anthropogenic due to the emissions of greenhouse gases, their precursors or other directly and indirectly radiatively active substances (e.g., water vapour from aircraft, which triggers contrails). In all scenarios considered by the IPCC the climate will warm, but at different rates and extends. In the Kyoto Protocol the various nations agreed to reduced the impact of men on climate. Unknown is the contribution of various sectors of human activity to climate change, i.e., the contributions from industry, households, aviation, surface traffic, agriculture, etc.. Various emissions are short lived and their impact on climate change may differ from an equivalent CO2 forcing. Furthermore, many indirect effect remain to be quantified, e.g., contrails and other anthropogenic cirrus clouds.
We concentrate on the climate change induced by traffic emissions, mainly from aviation and road traffic. First estimates of the aviation impact have been published in the IPCC Special Report "Aviation and the Global Climate". Apart from CO2 the knowledge to the quantitative climate effect is rather uncertain.
We currently quantify the radiative forcing from contrails. We have been able to develop a contrail parameterisation for use in GCMs (General Circulation Models) plus a treatment of thin (semi-transparent) clouds. These tools have been used in the ECHAM4.L39(DLR) GCM to diagnose the radiative forcing of contrails. In the next step we are going to use these parameterisations interactively in order to determine the climate impact of contrails in terms of temperature change or other meteorological variables
While the expected equilibrium climate change caused by well-mixed greenhouse gases (like CO2, CH4 or N2O) or by changes in the solar irradiance are proportional to the respective radiative forcing, this is not the case for species with geographically or vertically inhomogeneously distributed radiatively active species, e.g. from aircraft-induced ozone increase which is concentrated to the tropopause region of the northern hemisphere extra-tropics.
The climate sensitivity parameter is the link between the radiative forcing and the expected equilibrium change of the global mean (near) surface temperature.
The Lagrangian transport scheme ATTILA has been developed, which not only allows an efficient transport of many species without numerical diffusion, but which also enables very detailed transport studies, i.e., the determination of the spectrum of the age of air.
In a further effort new schemes for aerosol dynamics are implemented and the interaction of aerosols and clouds will be studied.