Simulated difference in mean annual precipitation

Simulated difference in annual mean precipitation (%) for the Midwest region, for each future time period (2021-2050, 2041-2070, and 2070-2099) with respect to the reference period of 1971-1999. These are multi-model means for the high (A2) and low (B1) emissions scenarios from the 14 (B1) or 15 (A2) CMIP3 global climate simulations. Color only (category 1) indicates that less than 50% of the models show a statistically significant change in precipitation. Color with hatching (category 3) indicates that more than 50% of the models show a statistically significant change in precipitation, and more than 67% agree on the sign of the change. Whited out areas (category 2) indicate that more than 50% of the models show a statistically significant change in precipitation, but less than 67% agree of the sign of the change (see text). Grid boxes whose centers are over the Great Lakes or outside the 8-state region are masked out. Generally, the models simulate increases in the north and east and little change or decreases in the southwest part of the region.