Urbanisation can significantly modify the physical properties of the landscape, and this is known to exert important influences on local meteorology. However, the potential interactions between urban meteorology and greenhouse gas-induced climate change have so far received little attention. Urban and non-urban areas are likely to exhibit different sentivities to greenhouse forcing, but this is generally not accounted for in climate change impacts studies. Increased urbanisation may itself provide an additional climate forcing, but the influence of this on past and future climate change outside the urban areas themselves has not yet been examined.

A new parametrization of urban areas has been implemented in the Hadley Centre General Circulation Model (GCM), to allow investigation of urban land surface processes in simulations of climate change and its impacts. The scheme is embedded within the MOSES2 land surface scheme, which calculates seperate energy balances for individual land surface types within each GCM gridsquare. It is therefore possible to diagnose the temperatures of urban and non-urban land separately. As an initial sensitivity study, climate simulations were performed with (i) current urban areas and (ii) with all urban areas replaced by non-urban land. The differences between the climates simulated with and without urban areas will be discussed.