Torrential Rains Dent Califonia's Worst Drought in at Least 1,200 Years

Torrential rains are falling across much of drought-scarred California, thanks to the wettest storm to affect the U.S. West Coast since at least October 2009. The heavy rains will put a noticeable dent in the state's three-year drought, which was the worst 3-year drought drought period in at least the past 1,200 years. This startling figure comes from a study of tree rings by researchers Daniel Griffin and Kevin Anchukaitis, How unusual is the 2012-2014 California drought?, published in December 2014 in Geophysical Research Letters (press release and supplemental photos available here.) The scientists used tree ring data from blue oak trees in southern and central California to infer soil moisture levels, and thus drought. Blue oak tree ring widths are particularly sensitive to moisture changes. According to the authors, these tree rings show that 2014 was California's worst single year for drought in at least 1,200 years. Interestingly, they found that the amount of precipitation during 2012 - 2014 was not the lowest on record--more extreme three-year low precipitation periods occurred in 1898 - 1900, and in 1527 - 1529. But because the period 2012 - 2014 was by far the warmest 3-year period in California history, these record warm temperatures "could have exacerbated the 2014 drought by approximately 36%," they said. This bodes ill for the future, since global warming will bring an increase in the odds of record warm temperatures, and California has shown it can naturally have less precipitation than they had the past three years.

More detailed blog posts made this week on the research attempting to quantify the potential human contribution to California's drought are available from Dana Nuccitelli at the Guardian's "Climate Consensus - the 97% blog, and from Dr. Michael Mann at Huffington Post.


Figure 1. 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.


Figure 2. Super Soaker: A massive drought-denting extratropical storm soaks the U.S. West Coast as seen in this 4 pm PST December 10, 2014 satellite image. Image credit: NASA/GSFC.

Yosemite Park waterfalls resume flowing
Yosemite National Park's big waterfalls--Yosemite Falls, Bridalveil Fall, and Cascade Fall--resumed flowing again on December 3 after two days of significant rainfall in California's Yosemite area. "To see Yosemite Falls coming to life this morning is truly exhilarating," stated Don Neubacher, Yosemite National Park Superintendent on December 3. "This is a wonderful time to visit Yosemite National Park and the waterfalls just add to the magnificence of the park." The falls slowed to a trickle in mid-July and were completely dry for most of August, September, October, and November due to California's exceptional drought. You can view the falls on the Yosemite Falls webcam. Today's rains are sure to make the waterfall roar big-time!


Figure 3. Yosemite Falls on December 4, 2014 after a round of heavy rains got them flowing again (top) and what the falls looked like on December 1, 2014 during the peak of California's record drought (bottom.) Image credit: Yosemite Conservancy.


Video 1. ‪NatureRelaxation.com‬ just released this beautiful high definition journey to the magnificent and rejuvenating Yosemite Falls, photographed in 2011.

I'm on the road today to rainy San Francisco, where I'll be visiting the WU main office and attending next week's American Geophysical Union conference. As a result, my posts will be a little irregular for the next ten days.

Jeff Masters