Robert R. Gillies
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Future Climates in Western North America
Robert R. Gillies, Utah Climate Center, Logan, UT
In the arid and semi-arid Western North America, observations of climate change point to an increase in average temperature that is greater than the rest of the world average. In line with such a warming trend in climate, several studies of the precipitation regime for the region have documented less snowfall as evidenced by decreases in snowpack as well as earlier snow melt, increased winter rain events and reduced summer flows. An ensemble of global climate model (GCM) projections for Western North America reflect just such conditions in that they suggest intensifying drying conditions to be the norm for the Southwest region due primarily to Hadley Cell intensification. Regions that lie to the Northwest, the GCMs have as benefiting from increased precipitation but in transitional zones, i.e., between the wetter and drier zones, any gains in projected precipitation are offset by the likelihood of an increased frequency of above normal temperatures during the summer months; such results in an overall deficit in water resources.