Simulated difference in the mean annual length of the freeze-free season

Simulated difference in the mean annual length of the freeze-free season for the Midwest region, for the 2041-2070 time period with respect to the reference period of 1980-2000 (top). Color with hatching (category 3) indicates that more than 50% of the models show a statistically significant change in the length of the freeze-free season, and more than 67% agree on the sign of the change (see text). Mean annual length of the freeze-free season for the 1980-2000 reference period (bottom left). Simulated mean annual length of the freeze-free season for the 2041-2070 future time period (bottom right). These are multi-model means from 8 NARCCAP regional climate simulations for the high (A2) emissions scenario. Grid boxes whose centers are over the Great Lakes or outside the 8-state region are masked out. The freeze-free season is simulated to become longer throughout the region, with increases mostly in the 20-30 day range.