The new study also examined the combined drought and heat conditions that happened during the 1930s drought that led to the Dust Bowl. That national tragedy was driven largely by lack of rainfall, which led to the air becoming hotter, and poor land management practices that caused astonishing dust storms, the scientists said. But recent dry-hot disasters are driven more by excess heat than a lack of rainfall.
So the triggering mechanism for heat-drought events is shifting, according to the researchers, from lack of rain to excess heat. The authors conclude that “if meteorological droughts of the length and severity observed in the 1930s occur during the hot years that are increasingly common in recent decades due to global warming, their concurrence can have devastating impacts.”
What’s more, they wrote, no major region of the continental United States is immune to severe droughts. They warn that the increased heat makes megadroughts more likely.
Perhaps most chillingly, they cite research that warns that the heat from climate change will increase demand for water and lead to scarcity.That could put strains on national infrastructure and society that, the scientists wrote, “ might push them to unprecedented states.”
A climate scientist who was not involved in the study, Daniel Swain of the University of California, Los Angeles, said the new research expands on previous work that focused on the West. The most important finding of the new paper, he suggested, was the increasing importance of heat as the driver of droughts.The warming global temperatures, he said, “are making it easier to achieve historically rare levels of dryness.”
Dr. Swain recently noted in a series of comments posted on Twitter that California, and possibly the Pacific Northwest as a whole, are likely to see another severe heat wave in early October, which could “bring extreme wildfire burning conditions once again.”
The new study, he said, does a good job of describing how drought and wildfire conditions spread and can occur over broad regions at the same time, making fire management much harder. “We are certainly seeing this with respect to wildfire in 2020,” he said.