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 simula ted 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 Stat es. The models simulate a smaller diurnal surface air temperature rang e, averaging overall 3.2 degrees C less than observed. Spring maxima a re consistently lower in the models by an average of 4.1 degrees C. Al though inadequate representation of clouds may contribute to the small er simulated temperature range, the underlying cause of the difference s 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 discr epancy is a matter of concern for the projection of future greenhouse- gas-induced climate changes and their impacts.