Climate responses under various anthropogenic and natural forcing scenarios have been studied and intercompared with several independent models and with different experimental strategies. The model simulated patterns of temperature and precipitation responses to increases in the greenhouse gas concentration are related to the model feedbacks, and therefore differ in detail between models. Nevertheless, some broad features of the responses with a surface- and lower troposheric warming in high latitudes, marked land-sea contrast with land warming more than the ocean surface, and intensified hydrological cycle (more evaporation and rainfall, with largest increases in the Tropics), are common to all models. The models produce a 10-15% increase of winter storm track activity over the north-western Europe at the time of CGydoubling. This increase is caused by an increasing baroclinicity over the entire north-east Atlantic with main changes occurring in the upper roposphere. In a warmer climate increases in storm intensity is due to a larger amount of water vapour in the atmosphere. The observed close relationship between the NAO index and the Atlantic storm track intensity is confirmed in the model simulations During the summer and winter season, the global mean convective rain rate decreases by about 4-5 % resulting from a strong decrease of the frequency of deep convective events. Globally, for rain rates between 5 and 40 mm/day a decrease of both frequency and the respective mean daily rain rates is found. However, for convective rain rates larger than 40 mm/day both frequency and mean daily rain rate increase indicating an increase of strong rain events. There is no agreement about the net influence of glacier mass gain in Antarctica and mass loss in Greenland on sea level change between the different simulations.
Cubasch, Ulrich
Allen, Myles
