Comparison of Observed Seasonal Temperature Maxima, Minima and Diurnal Range in North-America with Simulations from 3 Global Climate Models

Confidence in model projections of climate change requires reasonably realistic simulation of present-day climate (Wilson and Mitchell, 1987; Beer, 1992). Accordingly, we compare surface air temperatures simulated in the control runs of three general circulation models (Canadian Climate Centre, Oregon State University, United Kingdom Meteorological Office) with observations in three regions of the central United States. The models simulate a smaller diurnal surface air temperature range, averaging overall 3.2 degrees C less than observed. Spring maxima are consistently lower in the models by an average of 4.1 degrees C. Although inadequate representation of clouds may contribute to the smaller simulated temperature range, the underlying cause of the differences is unknown. Since increased minima and decreased diurnal ranges are the most widely observed features of surface air temperature over the Northern Hemisphere continents during the last four decades, the discrepancy is a matter of concern for the projection of future greenhouse-gas-induced climate changes and their impacts.