From the archives of Maven’s Notebook:
Original published on December 1, 2014
Dr. Dan Cayan is the director of the Climate Change Center at Scripps and also concurrently holds a research position in the USGS Water Resources division. At the November meeting of the Delta Stewardship Council, he gave an overview of California’s climate variability and of the current state of knowledge of the potential impacts of climate change on the state’s water resources.
Dr. Cayan began by presenting a slide showing precipitation by water year, going back to about the turn of the century. “The thing that is striking is the amount of ups and downs both on a year to year basis and also along the smooth curve there, there are episodes of relatively wet and relatively dry,” he said. “The last three years have been decidedly dry – actually the last 16 years or so. Since the late 1990s, we’ve been dry in California.”
He then presented a chart that shows the observed precipitation departure from 1998-99 through 2013-14. “If you tally this up, either gains or losses, the warm shadings are losses per year,” he said. “You can see the bulls eyes that occurs largely over California and Arizona. It is about a year and a half to over two and a half years of normal precipitation that we have not received over the 16 year period, so the point is that while these last three years have been quite dry, we’ve actually been subject more or less to dryness over this period, and really since the last really large El Nino that occurred in the Pacific basin in 1998.”
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