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Southwest and Central Plains Face Unprecedented Drought Risk in the 21st Century


Soybeans show the effects of ongoing drought in Navasota, Texas in 2013. The region is likely to become much drier in the next century. | USDA photo by Bob Nichols

SAN JOSE, California — A new study suggests the American Southwest and Central Plains will likely experience droughts worse than any in the last millennium, and it may be difficult for humans to adapt to the change.

Although it is well-established that global warming will exacerbate the ongoing drought situation in the American Southwest and Central Plains, the findings suggest that both regions will experience extended drought conditions in the future that will be more severe than even the hottest, driest megadroughts of the 12th and 13th centuries, an unusually warm period climatologists call the Medieval Climatic Anomaly.

It's believed that this extended period of severe drought may have contributed to the fall of the ancient Pueblos, a prehistoric Native American civilization that once lived in the region that is now the American Southwest.

"I was honestly surprised at just how dry the future is likely to be," said Toby Ault, an assistant professor in the department of earth and atmospheric sciences at Cornell University. "I look at these future megadroughts like a slow moving natural disaster. We have to put megadroughts into the same category as other natural disasters that can be dealt with through risk management."

The research appears in the inaugural issue of Science Advances.

“This paper looks at our future. And it’s a future I believe all of us as citizens need to pay attention to,” said Marcia McNutt, editor-in-chief of the new open access journal, at a press conference held at the 2015 AAAS Annual meeting.

Using drought records of the Medieval Period documented in the growth rings of trees, Ault and colleagues compared past climate reconstructions to 17 different computer model projections of 21st century climate. The results showed robust and consistent drying in nearly all the models, caused by a combination of reduced precipitation and warmer temperatures drying out the model soils. Notably, the results pointed to an extremely parched Southwest and Central Plains that will likely be drier than any other period of the past 1000 years.

“One thing that does come out of the projections is more extreme rainfall," Ault noted at the press conference. "The notion of a megadrought being a sustained period of below average precipitation might also be balanced with the expectation that when rain does come, there may be an abundance of it.”

The metrics used in the study could be useful for future water resource management and agricultural planning. In further studies, the researchers plan to study in detail individual drought events in the 21st century projections to glean insight into their future severity, persistence, and geographical scope.

"Understanding climates of the past provides a strong benchmark of natural variability, allowing us to better contextualize the magnitude of modern and future human-driven climate change, including contributions to extreme events such as droughts," said Benjamin Cook, lead author of the study and research scientist at NASA's Goddard Institute for Space Studies.