Thursday, December 18, 2014

Central CA Blue Oak trees record worst 3 year drought in 1200 years

Pencil-like tree-ring cores are collected non-destructively using a Swedish increment borer in May, 2014. (Daniel Griffin/University of Minnesota)
Non-destructive tree-ring core collection measures
extreme 3 year drought (from 2012):
lack of rain + record high temperatures
San Jose Mercury News/Science and Environment/Paul Rogers, 12/5/2014.  "California drought the worst in 1,200 years, new study says."   ".... Analyzing tree rings that date back to 800 A.D. -- a time when Vikings were marauding Europe and the Chinese were inventing gunpowder -- there is no three-year period when California's rainfall has been as low and its temperatures as hot as they have been from 2012 to 2014, the researchers found. ....

The report, published in the journal of the American Geophysical Union, was written by researchers at Massachusetts' Woods Hole Oceanographic Institution and the University of Minnesota. .... The researchers compared the information to a database of other tree ring records from longer-living trees like giant sequoias and bristlecone pines, dating back 1,200 years."   Read article.

Related - KQED/Science/Alex Emslie, 12/4/14. "Study: California drought most severe dry spell in at least 1,200 years." .... “California’s old blue oaks are as close to nature’s rain gauges as we get,” said Griffin, a NOAA Climate and Global Change Fellow with Woods Hole Oceanographic Institution. “They thrive in some of California’s driest environments.”  The researchers collected their own blue oak tree-ring samples from south and central California, giving them a pretty good idea of yearly precipitation in the area back to 1293. They then augmented their samples with data from the North American Drought Atlas and the National Oceanic and Atmospheric Administration Palmer Drought Severity Index.  

The result: The study estimates that in the past 1,200 years, there have been 66 dry periods lasting three-to-nine years and 37 more-severe, three-year droughts. But not one of them has been as extreme as the one beginning in 2012, despite some years in the past seeing similarly low precipitation. It’s not only lack of rain that makes a drought, though. Record-high temperatures added to California’s strife to make this dry spell the worst in more than 1,000 years, according to the study. The researchers estimate high temperatures have intensified the drought by about 36 percent. UC Berkeley geology professor and researcher Lynn Ingram said the study’s findings appear solid."   

Note:  photograph  from this article, caption:  "Pencil-like tree-ring cores are collected non-destructively using a Swedish increment borer in May, 2014 (Daniel Griffin/University of Minnesota).   

Posted by Kathy Meeh

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