Status and improvements of coupled general circulation models

Coupled general circulation models (CGCMs) integrate our knowledge about atmospheric and oceanic circulation, Different versions of CGCMs are used to provide a better understanding of natural climate variability on interannual 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 intercomparisons, new test data (mainly from satellites), more powerful computers, and parameterizations of atmospheric and oceanic processes have improved CGCM performance to such a degree that the model results are now used by many decision-makers, including governments. They are also fundamental for the detection and attribution of climate change.