ausblenden:
Schlagwörter:
anthropogenic effect; Arrhenius; climate change; global warming; greenhouse effect; greenhouse gas; numerical model, Arrhenius
Zusammenfassung:
Results are presented from a recent high resolution transient climate change experiment carried out at the Max Planck Institute for Meteorology, Hamburg. The experiment is discussed in the light of the greenhouse warming experiment by Arrhenius. The transient calculation started in January 1860 and continued until the end of the 21st century. The effect of individual greenhouse gases has been incorporated using observed data until 1990 and thereafter assumed emissions according to (IPCC) scenario IS92a. Validation of the coupled model shows a realistic simulation of observed coupled modes such as El Nino-Southern Oscillation. The simulated low frequency variability at middle and high latitudes resembles, by and large, the observed one. A detailed evaluation over Scandinavia shows that the model reproduces the typical very strong interannual variability of this region. The result shows a small warming until present in broad agreement with observations. There is a strong positive feedback with water vapor but a negative feedback with clouds. The evaluation is concentrated at the time the concentration of the greenhouse gases has doubled compared to the starting time. Such a doubling is expected to take place in 2030-2040. The energy cycle is slowly changing and a gradual increase in the absorption of short-wave radiation in the atmosphere and an increase in the net long-wave radiation at the ground are noted. The latent heat flux from the surface of the earth increases while the sensible heat flux decreases. The hydrological cycle increases very slowly and mainly over land. After 1990, a rapid warming is starting which goes on with superimposed minor multidecadal variations until the end of the run. Overall global warming amounts to some 3.5°C for the period 1990 to 2100. At the time of greenhouse gas doubling, the global warming amounts to 1.9°C. The typical feedback pattern for the early part of the run continues with increasing amplitude and so do the changes in the hydrological cycle. The warming pattern shows a strong amplitude in the Arctic associated with a marked retreat of Arctic sea ice. The overall warming over the Scandinavian area is one to two degrees higher than the global average superimposed upon a similar high interannual variability as in the present climate.
