Study: California drought most severe dry spell in at least 1,200 years

California’s current drought is pretty exceptional — like the driest in about a millennium — according to an article published today in the journal Geophysical Research Letters by scientists with the University of Minnesota and Woods Hole Oceanographic Institution in Massachusetts. But how could they know that? There weren’t a lot of rain gauges in California in 800 A.D. — at least, not the plastic kind. So authors Daniel Griffin and Kevin Anchukaitis looked to tree-ring samples from California blue oaks. 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. 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. <more>

Dec. 4, 2014 KQED