Photo Credit: Robert Couse-Baker | CC BY 2.0
"While 3-year periods of persistent below-average soil moisture are not uncommon," geoscientists Daniel Griffin, of the University of Minnesota, and Kevin Anchukaitis, of Woods Hole Oceanographic Institute, write in the latest issue of Geophysical Research Letters, " the current event is the most severe drought in the last 1200 years."
[Griffin and Ahchukaitis] reconstructed California's temperature and precipitation history back to 800 A.D. using tree ring data. Hidden in this millennium of data they found as many as 66 dry periods of at least three to nine years. In the entire 1,200 year period they studied, there were only three droughts that were similar in nature to the current drought.
Read the full scientific study at Geophysical Research Letters.