Tree Rings Don’t Lie: It’s the Worst California Drought in at Least 1,200 Years

Monday, December 08, 2014
(photo: Bert Kaufmann/Flickr)

Can California’s biggest storm in two years end its worst drought in at least 1,200 years?

Uh, no. That would probably take another eight storms just like it, Art Hinojosa, chief of hydrology at the state Department of Water Resources, told the San Jose Mercury News.

Although California has experienced 37 three-year periods of drought into the last millennium, the state did not suffer the same severe temperatures and low precipitation in the past. What we are experiencing is very different, according to a study published last week in the American Geophysical Union by researchers at Massachusetts' Woods Hole Oceanographic Institution and the University of Minnesota.  

The severity “was a surprise,” co-author Kevin J. Anchukaitis told the Los Angeles Times. “I don’t think we expected to see that at all.”

There were times in the past when California received less rain during a three-year drought, including the early 16th and 20th centuries. But they weren’t this hot. Heat exacerbates low precipitation and the researchers calculated this drought was 36% worse because of it.

The researchers reached their conclusions after analyzing tree rings in Central and Southern California dating back to 800 A.D. They studied 278 blue oaks, whose ring widths reflected precipitation, and cross-referenced that information with rainfall records from the National Oceanic and Atmospheric Administration. They also tapped the Palmer Drought Severity Index and the North American Drought Atlas for data.    

As of December 2, a tiny piece of Del Norte County, just below the Oregon border, registered as “abnormally dry” on the Drought Monitor. The rest of the state, 97.2%, was worse. Three quarters were experiencing “extreme drought” and half had “exceptional drought.”

The rain helps, but the researchers said that 44% of three-year droughts have historically lasted at least four years, and that was before humans turned up the planet’s heat.

“There is no doubt that we are entering a new era where human-wrought changes to the climate system will become important for determining the severity of droughts and their consequences for coupled human and natural systems,” Anchukaitis said.

–Ken Broder  


To Learn More:

California Drought the Worst in 1,200 Years, New Study Says (by Paul Rogers, San Jose Mercury News)

California Floods During Worst Drought in 1,200 Years (by Doyle Rice and Trevor Hughes, USA Today)

California Drought Most Severe in 1,200 Years, Study Says (by Matt Stevens, Los Angeles Times)

Evidence Suggests California's Drought Is the Worst in 1,200 Years (Woods Hole Oceanographic Institution)

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