Future Climate Scenarios for Semiarid Farming Regions of North America.

Semi-arid climates characterize a large but discontiguous fraction of the western half of the US. These climate regions support a large fraction of US commodity crops (primarily wheat) and specialty crops. Agriculture in much of the region relies on irrigation. A general outcome of simulations of future scenario climates is that dry areas will become drier and hotter and wet areas will become wetter and more humid. A noticeable pattern of recent shifts in climate suggests that, for a given location, dry periods also will become drier and hotter and wet periods also will become wetter and more humid. However, for any given semi-arid location these trends may not be linear or monotonic. Future temperatures of these regions will generally increase, but precipitation may increase or decrease depending on location. Northern semi-arid regions likely will see increased precipitation, while southern semi-arid regions will experience more drying. Impacts on agriculture will be highly dependent on changes in availability and timing of irrigation water. Some regions that currently are home to specialty crops may experience climate changes that exceed physiological limits for such crops. Shifts in seasonality also may be disruptive for currently grown crops. For these reasons, strategies for adapting to climate change will be highly location dependent, complex, and subject to modification over time.