Physical Understanding of Human-Induced Changes in U.S. Hot Droughts Using Equilibrium Climate Simulations

Our analysis of climate simulation finds that summertime drought-heatwave relationships change significantly over the southern and southwest U.S. due to man-made climate change since the late 19th century.

Linyin Cheng, assistant professor of geosciences, University of Arkansas

• Although the link between droughts and heat waves is widely recognized, how climate change affects this link remains uncertain.
• Assesses how, and by how much, human-induced climate change affects summertime hot drought compound events over the contiguous United States
• Derives results by comparing hot drought statistics in long simulations of a coupled climate model (CESM1) subjected to year-1850 and year-2000 radiative forcings
• Finds a strong and nonlinear dependency of heat-wave intensity on drought severity within each climate state in water-limited regions of the southern Great Plains and southwestern United States
• Finds that heat-wave intensity is insensitive to drought severity in energy-limited regions of the northern and/or northeastern United States
• Finds that anthropogenic warming leads to enhanced soil moisture–temperature coupling in water-limited areas of the southern Great Plains and/or southwestern United States and consequently amplifies the intensity of extreme heat waves during severe droughts
• Finds that this strengthened coupling accounts for a substantial fraction of rising temperature extremes related to the long-term climate change in CESM1, highlighting the importance of changes in land–atmosphere feedback in a warmer climate
• Finds, in contrast, that coupling effects remain weak and largely unchanged in energy-limited regions, thereby yielding no appreciable contribution to heat-wave intensification over the northern and/or northeastern United States apart from the long-term warming effects