How unusual is the 2012-2014 California drought? 

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Dan Griffin Daniel Drought Tree Rings Minnesota Dendrochronology California

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The 2012-2014 California drought, unusual in the context of the last 1,200 years, greatly diminished water reserves in Lake San Antonio of the upper Salinas Valley. May 2014 image by Daniel Griffin.


Pencil-like tree-ring cores are collected non-destructively using a Swedish increment borer. May 2014 image by Daniel Griffin.


 
The 2012-2014 California drought, unusual in the context of the last 1,200 years, greatly diminished water reserves in Lake Nacimiento of the upper Salinas Valley. May 2014 image by Daniel Griffin.

Kevin Anchukaitis (left) and Daniel Griffin (right) used tree-rings from centuries-old blue oak like the one pictured to provide long-term context for the ongoing California drought. 2014 image by Megan Lundin.


Blue oak trees up to 500 years old thrive in California's drought-scorched foothills. Their rings provide a unique record of drought and wetness for the Golden State. February 2014 image by Daniel Griffin.

Oaks in California can live for up to 500 years and samples from dead logs can be used to extend the record back in time up to 700 years. Patterns of narrow and wide rings correspond to years of drought and wetness. May 2014 image by Daniel Griffin.

Blue oak trees up to 500 years old thrive in California's drought-scorched foothills. Their rings provide a unique record of drought and wetness for the Golden State. 2014 image by Daniel Griffin.


Kevin Anchukaitis collects an tree-ring sample from a 300-year old blue oak in California. 2014 image by Daniel Griffin.

Daniel Griffin collects a tree-ring sample from a dead tree, which can be used to extend the tree-ring record back in time up to 700 years. 2014 image by Kevin Anchukaitis.


Kevin Anchukaitis collects an tree-ring sample from a 300-year old blue oak in California. 2014 image by Daniel Griffin.



Tree-ring scientist Daniel Griffin measures a 400-year old blue oak in California. 2004 image by David Stahle.


Some oak trees are struggling to survive in California's drought-scorched foothills. 2014 image by Daniel Griffin.



Daniel Griffin collects a tree-ring sample from a dead tree, which can be used to extend the tree-ring record back in time up to 700 years. 2014 image by Kevin Anchukaitis.


Blue oak trees often live for 300-500 years in California's foothills and their annual growth rings provide a unique record of drought and wetness for the Golden State. 2014 image by Daniel Griffin.


Researchers collect a tree-ring sample from a 450-year old blue oak tree in the southern San Joaquin Valley. 2014 image by Daniel Griffin.


Researchers prepare to collect tree-ring samples from sample centuries old-blue oaks in the southern San Joaquin Valley. 2014 image by Daniel Griffin.