Modellierung und Analyse der Sensitivitaet des Klimasystems gegenueber anthropogenen Stoerungen Abschlussbericht

Using a hierarchy of atmospheric general circulations (GCMs) and coupled atmosphere-ocean models, simulations of the present climate have been performed and also of the future climate as it may evolve from the expected increase of greenhouse gases in the atmosphere. The atmospheric model has been used especially for studying the impact of observed tropical and extratropical sea surface temperature anomalies on the interannual variability of the extratropical circulation. Furthermore, the impact of clouds on climate sensitivity has been studied with different atmospheric GCMs. The atmospheric GCM coupled to a slab ocean model has been used to study the climate equilibrium response to CO2 doubling and anthropogenic sulfate aerosol. It has been demonstrated for the first time that anthropogenic sulfur emissions have a potentially strong impact on climate. Although the radiative forcing due to current (1980) sulfate aerosols amounts only to about 30% of the greenhouse gas forcing at the same time, its climate effect is relatively strong due to amplification by nonlinear feedback processes. The main emphasis was devoted to the development of a coupled ocean-atmosphere GCM as a tool for climate prediction. The model that has been developed within this project is able to capture a significant amount of the observed natural variability such as the El Nino/Southern Oscillation (ENSO) phenomenon. The predicted global warming on the basis of the IPCC scenario A ('business as usual') is about 0.3 C per decade during the next century. The spatial distribution differs from the equilibrium response particularly in areas of deep water formation, such as in the North Atlantic and around Antarctica, where efficient vertical mixing is able to delay the temperature response significantly, as compared to more traditional slab ocean models. (orig.)Available from TIB Hannover: F96B332+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman