Study: heat, not lack of precipitation, is driving western U.S. droughts

Drought conditions at Lake Oroville in 2014. Credit: NOAA

Higher temperatures caused by anthropogenic climate change made an ordinary drought into an exceptional drought that parched the American West from 2020-2022, according to a new study by UCLA, NOAA and CIRES scientists. 

The scientists found that evaporative demand, or the thirst of the atmosphere, has played a bigger role than reduced precipitation in droughts since 2000. During the 2020-2022 drought, evaporation accounted for 61% of the drought’s severity, while reduced precipitation only accounted for only 39%.

“Research has already shown that warmer temperatures contribute to drought, but this is, to our knowledge, the first study that actually shows that moisture loss due to demand is greater than the moisture loss due to lack of rainfall,” said Rong Fu, a UCLA professor of atmospheric and oceanic sciences and the corresponding author of the study, which was published in the journal Science Advances.