Integrated Assessment as a Step toward Reducing Climate Vulnerability in the Southwestern United States

NOVEMBER 2004 AMERICAN METEOROLOGICAL SOCIETY | T he southwestern United States exhibits considerable interannual and interdecadal variability in climate (Sheppard et al. 2002), with over tenfold differences in winter precipitation from year to year.1 Summer monsoons and winter storms create a bimodal precipitation pattern. Winter precipitation is particularly important, because it provides much of the streamflow and groundwater recharge that both replenish water supplies and maintain important ecosystems. The region’s economy and lifestyle are highly vulnerable to this variability in climate. Municipal, industrial, and agricultural sectors depend, at least in part, on highly variable surface water supplies, and on aquifers that are being depleted in many parts of the region. Current approaches to managing forests, grazing land, surface waters, and riparian areas assume consistent seasonal and interannual precipitation.2 Links between Southwest climate and measurable patterns in the Pacific Ocean (Sheppard et al. 2002) allow significant predictability of seasonal precipitation and temperature in the region, particularly for the winter half-year. There are also signs that global warming could lead to changes in the climate of the region, including an increased frequency of extreme wet and dry periods (National Assessment Synthesis INTEGRATED ASSESSMENT AS A STEP TOWARD REDUCING CLIMATE VULNERABILITY IN THE SOUTHWESTERN UNITED STATES