Severe Ancient Droughts: A Warning to California

http://www.nytimes.com/1994/07/19/science/severe-ancient-droughts-a-warning-to-california.html

But between 900 and 1400 A.D., during the'Medieval Warm Period,' there were a couple of droughts that were over a century long," said B. Lynn Ingram, professor of Earth and planetary science and geography at the University of California, Berkeley, and co-author of the bookThe West Without Water: What Past Floods, Droughts, and Other Climatic Clues Tell Us About Tomorrow.

http://news.nationalgeographic.com/news/2014/02/140214-drought-california-prehistory-science-climate-san-francisco-2/