Antarctica and environmental change - The response of Antarctic climate in general circulation model experiments with transiently increasing carbon dioxide concentrations

Coupled models of the atmosphere-ocean and land surface provide important tools for prediction of climate change. The results of experiments carried out at the Hadley Centre, Meteorological Office, in which such models have been used in studies of climate change due to increased levels of greenhouse gas concentrations are described, with particular reference to simulation of climate change in the region of Antarctica. Although, as yet, the ability of such models to represent regional climate change is relatively low, processes in the southern ocean around Antarctica are important for determining the global pattern of transient temperature change as CO2 increases. This is illustrated by results from two experiments. Firstly, an experiment with a high resolution (2.5° x 3.75°) atmospheric model coupled to a simple slab ocean in which the response of climate to an instantaneous doubling of greenhouse gas concentrations was examined, and which showed the largest induced warming to be in the polar regions in winter similar to the results of previous experiments carried out at the Meteorological Office and elsewhere. However, an experiment with a deep ocean model and a (more realistic) 1% per annum increase in greenhouse gas concentrations shows the pattern of global warming to be shifted to give minimum values around Antarctica as a result of deep oceanic mixing similar experiments carried out at other centres