General circulation model experiments on the climatic effects due to a doubling and quadrupling of carbon dioxide concentration

A global, spectral atmospheric general circulation model (GCM) with an energy balance ocean formulation, sometimes referred to as a swamp ocean, and realistic geography is run for doubled and quadrupled the present amount of atmospheric carbon dioxide, CO//2, with fixed and computed clouds. All experiments are compared to control runs with the present amount of CO//2. The experiments use annually averaged solar forcing; thus, there is not a seasonal cycle. The results indicate warming due to increased CO//2 is smaller than that found in other studies with swamp-ocean models coupled to atmospheric GCMs. One possible explanation may be attributed to large differences in the various models used, especially with regard to snow-sea ice albedo parameterizations.