Future Projections of Heat and Fire-Risk Indices for the Contiguous United States

Abstract

ncreasing temperatures and changes in precipitation associated with climate change are expected to have increasing impacts on the contiguous United States in the coming decades, including military training and outdoor activities in general. Projections of daily temperature and precipitation from multiple global climate model projections are used to calculate the days with high heat and drought indices, which also indicate heat-related illness and fire risks. The heat stress index [the wet-bulb black-globe temperature (WBGT)] and drought index (Keetch?Byram drought index) are calculated from climate model projections from 1950?99 and 2070?99 and compared with those calculated from observed weather data for stations across the contiguous United States. Significant increases are projected across the southern United States for the days in the high index category above 32.2°C and high drought category. The higher humidity of the southeastern United States contributes to high WBGT as well, while the air temperatures are greatest in the Southwest. The highest WBGT categories occur for the daytime maximum; however, daily minimum WBGTs in the restricting category also are projected for more than 50 days per year in the Southeast. The high drought index is projected to increase across the Great Plains and the central and southern United States, affecting wildfire risks for military and public lands, including large agricultural regions. These projected impacts can be characterized as widespread and severe for large portions of the United States, with expected impacts to military planning, public health and safety, and natural resource management.