Drought has scorched western North America for the better part of two decades, withering crops, draining rivers and fueling fires. Scientists now warn that this trend could be just the beginning of an extended megadrought that ranks among the very worst of the past 1,200 years and would be unlike anything known in recorded history.

As with past megadroughts, the current event is driven largely by natural variations in climate. But unlike prehistoric megadroughts, it’s happening during an era of climate change that the authors say is responsible for nearly half of its destructive impact.

Megadroughts, by definition, are occasional events of unusual severity lasting for at least 20 years. During the past 1,200 years, four major megadroughts occurred in the American West: during the 800s, the mid-1100s, the 1200s, and the late 1500s.

Now the new research reveals that the period of drought between 2000 and 2018 was the second driest of all 19-year periods in the past 1,200 years. “Suddenly, looking at the data since 2000, they’re definitely suggesting that we are currently on a megadrought trajectory,” Smerdon says. And while 20 years is a long time to live with drought, the megadroughts recorded in the paleorecord lasted far longer, like 50 or even 90 years.

https://www.smithsonianmag.com/science-nature/american-west-may-be-entering-megadrought-worse-any-historical-record-180974688/