Warming climate intensifes summer drought in parts of US

Linyin Cheng, assistant professor of geosciences, used data from the National Center for Atmospheric Research's Community Earth System Model to study summer droughts that occurred both before and after the Industrial Revolution. Cheng and colleagues from the National Oceanic and Atmospheric Administration and universities in China and Colorado ran simulations to assess how, and by how much, human-induced climate change affects summer heatwaves in the contiguous United States. The study was published in the Journal of Climate.

The researchers found that in places with low moisture in the soil, such as the southern plains and southwest, higher temperatures brought about by climate change led to an increased "coupling" of land and atmosphere, which further increased the severity of heatwaves. In places with more moisture in the soil, such as the northeast, they found no appreciable coupling and therefore no contribution to heatwave intensification.

"Our analysis of climate simulation finds that summertime drought-heatwave relationships change significantly over the southern and southwest U.S. due to human-made climate change since the late 19th century," said Cheng. "By contrast, the drought-heatwave relationship over northern U.S regions undergoes little change in the warmed climate."

The findings raise the idea of a self-reinforcing climate loop: as a region's climate becomes more arid due to climate change, droughts become hotter, further reducing soil moisture.

"Overall, these results indicate that strengthened land-atmosphere feedback is a significant physical driver for increasing occurrences of drought-related extreme heatwaves, particularly over the semi-arid and arid regions of the United States," the report states.