Why the intense U.S. drought is now a megadrought

BY MARK KAUFMAN

Climate 101 is a Mashable series that answers provoking and salient questions about Earth’s warming climate. 

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The water keeps going down.

Almost the entire Southwest is mired in various stages of drought as of April 21, 2021, resulting in falling water levels at the nation’s two largest reservoirs, Lake Mead and Lake Powell. The consequences could be unprecedented. For the first time in Lake Mead’s 85-year existence, water levels may drop below a point this summer that triggers water cuts in Arizona and Nevada. (This would largely mean cuts to farmers and agriculture.)

Geological and climate records show that sustained droughts, lasting decades, come and go in the Southwest. But the current prolonged drying trend, which started some 20 years ago, is exacerbated by a rapidly warming climate. This makes the current drought not just long, but especially intense. 

“It’s two decades long and probably the worst drought in at least 400 years,” said Benjamin Cook, a research scientist at Columbia University’s Lamont-Doherty Earth Observatory who studies drought. 

The big picture is clear. In the last 50 years, precipitation trends in the Southwest haven’t changed much and remained mostly flat, explained Jonathan Overpeck, a climate scientist at the University of Michigan who researches Southwestern drought. Yet, the amount of water flowing in the region’s major artery, the Colorado River, has dropped significantly — by 16 percent — in the last century. The land is drying out, too. “The only thing that’s changing in a big way is temperature,” said Overpeck. …...more here

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