Comparison of GCM-projected daily maximum and minimum temperature for the Great Lakes Region

Climate projections from different GCMs can vary substantially. These differences are often best expressed at the regional level, particularly for regions such as the Great Lakes with strong local influences on climate. Differences in GCM projections contribute to the difficulty of developing appropriate scenarios for assessment research, and complicate the comparisons of assessment studies that have employed simulations from different GCMs . In this analysis, we compare daily simulations of maximum and minimum temperature from one of the GCMs chosen for the U.S. National Assessment (e.g., the HadCM2) to similar simulations from four other GCMs (CCMI, UKTR, GISS, and MPI) and to high-quality observational records. The comparisons are conducted for current conditions (1960-1989) and for a 2xCO2 environment (approximately 2040-2059) at six lake-influenced locations in the Great Lakes region. In addition, the temperature series are used to calculate several ecologically-significant indices and threshold parameters which are then compared for the different GCMs.