Have we been living in a megadrought?

Catalina Mountains
In the Catalina Mountains in southern Arizona, forests struggle to keep up with recent increases in drought and wildfire activity, which are expected to continue due to human-caused climate change. (Park Williams / Lamont-Doherty Earth Observatory)

A comparison of weather records since 2000 with similar time frames in past centuries has led researchers to conclude that we’re in the midst of a megadrought of historic proportions.

The assessment draws upon tree-ring data from nine Western states, stretching from Oregon and Idaho down through California and New Mexico, plus part of northern Mexico. The patterns in the tree rings served to track annual soil moisture going back to the ninth century.

Researchers saw evidence for dozens of droughts across the region over the centuries, but four periods of extreme aridity stood out, in the late 800s, the mid-1100s, the 1200s and the late 1500s. The fourth megadrought, which lasted from 1575 to 1603, was the worst of the bunch.

Since then, there have been no droughts on that scale. Until now.

In this week’s issue of the journal Science, the research team reports that the 19-year period beginning in the year 2000 has been almost as dry as the worst 19-year period of the 1575-1603 megadrought, based on soil moisture readings.

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By Alan Boyle

Mastermind of Cosmic Log, contributor to GeekWire and Universe Today, author of "The Case for Pluto: How a Little Planet Made a Big Difference," past president of the Council for the Advancement of Science Writing.

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