Future changes of the atmospheric composition and the impact of climate change

The development of the future atmospheric chemical composition is investiga ted with respect to NOy and O-3 by means of the off-line coupled dynamic-ch emical general circulation model ECHAM3/CHEM. Two time slice experiments ha ve been performed for the years 1992 and 2015. which include changes in sea surface temperatures. greenhouse gas concentrations. emissions of CFCs, NO x and other species. i.e., the 2015 simulation accounts fur changes in chem ically relevant emissions and for a climate change and its impact on air ch emistry. The 2015 simulation clearly shows a global increase in ozone excep t for large areas of the lower stratosphere, where no significant changes o r even decreases in the ozone concentration are found. For a better underst anding of the importance of (A) emissions. like NOx and CFCs. ( B) future c hanger of air temperature and water vapour concentration. and (C) other dyn amical parameters, like precipitation and changes in the circulation diabat ic circulation. stratosphere-troposphere-exchange. the simulation of the fu ture atmosphere has been performed stepwise. This method requires a climate -chemistry modal without interactive coupling of chemical species. Model re sults show that the direct effect of emissions (A) plays a major role for t he composition of the future atmosphere, but they also clearly show that cl imate change (B and C) has a significant impact and strongly reduces the NO , and ozone concentration in the lower stratosphere.