Past megadroughts hit North and South America in tandem

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Science Magazine | Paul Voosen
January 03, 2020

For 10 years, central Chile has been gripped by unrelenting drought. With 30% less rainfall than normal, verdant landscapes have withered, reservoirs are low, and more than 100,000 farm animals have died. The dry spell has lasted so long that researchers are calling it a “megadrought,” rivaling dry stretches centuries ago. It’s not so different from the decade-long drought that California, some 8000 kilometers away, endured until this year.

By analyzing tree ring records, scientists have now found evidence that such tandem droughts are more than a coincidence: They are surprisingly common over the past 1200 years, and they may often share a common cause—an abnormally cool state of the eastern Pacific Ocean known as La Niña. “We did not expect there to be as much coherence as we see,” says Nathan Steiger, a paleoclimatologist at Columbia University who presented the work this month at a meeting of the American Geophysical Union. “They just happen together.” The results suggest that, in the future, extreme aridity could strike all along the Americas’ western coast.  Read More