Climate Change-Driven Megadrought Likely to Hit Western U.S., Study Says

Global warming may lead to the worst drought recorded in history.
Fabienne Lang

Climate change has brought about a number of alarming impacts on our environment, and those living in the western states of the U.S. will have felt quite a few of them over the last few years.

Since the early 2000s the region from northern Mexico all up the western U.S. coast has experienced extreme heat conditions, and now researchers from Columbia University are warning of a megadrought worse than any previously recorded, brought around due to climate change.

The study was published in Science on Friday.


Extreme long-term drought

The Columbia study focused on modern weather observations, 1,200 years' worth of tree-ring data and dozens of climate models to reach the conclusion that a megadrought as bad or worse than any yet recorded is most likely in progress in the western states of the U.S. 

Climate Change-Driven Megadrought Likely to Hit Western U.S., Study Says
The Catalina Mountains' forests in Arizona struggle with increased drought and wildfire activity, Source: Park Williams/Lamont-Doherty Earth Observatory

"Earlier studies were largely model projections of the future," said lead author Park Williams, a bioclimatologist at Columbia University’s Lamont-Doherty Earth Observatory. "We’re no longer looking at projections, but at where we are now. We now have enough observations of current drought and tree-ring records of past drought to say that we’re on the same trajectory as the worst prehistoric droughts."

Studying tree rings enables scientists to infer yearly soil moisture for centuries even before humans started impacting the climate. This study is the most up-to-date and all-encompassing long-term analysis of the subject. The area the study focuses on spans from northern Mexico, up through California, Oregon, and across to Montana, covering nine states in total. 

The authors of the study stressed that the importance is not necessarily to do with the drought's severity, rather that it's due to climate change that this megadrought has been brought on. "It doesn’t matter if this is exactly the worst drought ever," said co-author Benjamin Cook, who is affiliated with Lamont and the Goddard Institute for Space Studies.

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Climate Change-Driven Megadrought Likely to Hit Western U.S., Study Says
Areas of southwestern U.S. affected by drought in the early 2000s, Source: Adapted from Williams et al./Science, 2020

"What matters is that it has been made much worse than it would have been because of climate change." As temperatures are expected to continue rising, it is likely the drought will continue for the foreseeable future; or briefly fade only to return later on, explain the researchers.

"Because the background is getting warmer, the dice are increasingly loaded toward longer and more severe droughts," said Williams. "We may get lucky, and natural variability will bring more precipitation for a while. But going forward, we’ll need more and more good luck to break out of drought, and less and less bad luck to go back into drought."

Williams stressed that it may be conceivable that the area could remain arid for centuries. "That’s not my prediction right now, but it’s possible," he said.

Yet another wake-up call with regards to climate change.


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