Future western U.S. ‘megadroughts’ could be worse than ever

George H. H. Huey/Corbis

Future western U.S. 'megadroughts' could be worse than ever

SAN JOSE, CALIFORNIA—The sandstone ruins of Chaco Canyon, New Mexico—a once thriving settlement abandoned in the 13th century by the ancient Pueblo peoples during a 60-year-long "megadrought"—serve as a silent reminder that when water supplies dwindle, even sophisticated societies may not be able to adapt. Now, new research presented today at the AAAS (which publishes Science) meeting here, and published in this week's issue of Science Advances, suggests that the decades-long megadroughts that hit the southwestern and midwestern United States over the past millennium may have been a mere preview of droughts to come as a result of climate change. The study's analyses of projected soil moisture over the next 100 years, based on 17 state-of-the art climate models, bolster previous research suggesting that droughts will intensify as the climate warms. And when compared with a 1000-year reconstruction of past droughts based on more than 1800 tree-ring chronologies collected across the continent, droughts forecast by nearly every one of those models are "unprecedented," even  if CO2 emissions are dramatically reduced, researchers say. Under a “business-as-usual” emissions scenario, they add, there’s an 80% likelihood that at least one decades-long megadrought will hit the regions between 2050 and 2100.

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