Status and improvements of coupled general circulation models

Coupled general circulation models (CGCMs) integrate our knowledge about at mospheric and oceanic circulation, Different versions of CGCMs are used to provide a better understanding of natural climate variability on interannua l and decadal time scales, for extended weather forecasting, and for making seasonal climate scenario projections. They also help to reconstruct past climates, especially abrupt climate change processes. Model intercomparison s, new test data (mainly from satellites), more powerful computers, and par ameterizations of atmospheric and oceanic processes have improved CGCM perf ormance to such a degree that the model results are now used by many decisi on-makers, including governments. They are also fundamental for the detecti on and attribution of climate change.