Future U.S. wildfire potential trends projected using a dynamically downscaled climate change scenario

Abstract

This study investigates trends in wildfire potential in the continental United States under a changing climate. Fire potential is measured by the Keetch–Byram Drought Index (KBDI), which is determined by daily maximum temperature and precipitation. The impact of relative humidity and wind speed is examined by comparing KBDI with the modified Fosberg Fire Weather Index (mFFWI). The present (1971–2000) and future (2041–2070) daily regional climate conditions were obtained by dynamical downscaling of the HadCM3 global projection using HRM3 regional climate model provided by the North America Regional Climate Change Assessment Program (NARCCP). It is shown that fire potential is expected to increase in the Southwest, Rocky Mountains, northern Great Plains, Southeast, and Pacific coast, mainly caused by future warming trends. Most pronounced increases occur in summer and autumn. Fire seasons will become longer in many regions. The future fire potential increase will be less pronounced in the northern Rocky Mountains due to the changes in humidity and wind. Present fire potential is found to have been increasing across continental U.S. in recent decades. The future KBDI increase in the central Plains and the South projected using the HadCM3–HRM3 climate change scenario is smaller than the increases using the climate change scenarios from most of other NARCCAP model combinations. Larger inter-seasonal and inter-annual fire potential variability is expected in the future in the Pacific and Atlantic coastal regions. The projected increases in wildfire potential for many regions of the U.S. suggest that increased resources and management efforts for disaster prevention and recovery would be needed in the future.