A security guard walks the perimeter of the Almaden Reservoir on January 28, 2014 in San Jose, California. (Justin Sullivan/Getty Images)
A security guard walks the perimeter of the Almaden Reservoir on January 28, 2014 in San Jose, California. (Justin Sullivan/Getty Images)

Climate change is making the weather pattern that’s responsible for California’s drought more likely, according to a new study from Stanford.

The phenomenon, known as the “ridiculously resilient ridge,” is a huge, hard bubble of high pressure air parked in the Pacific Ocean. In the rainy season, it pushes storms that could’ve been headed to California up north, to Canada. High pressure ridges that cause California to dry out happen naturally — there have been plenty of long droughts in the past — but climate change is likely to make them more frequent, according to the study published Monday in the Bulletin of the American Meteorological Society. Swain’s study was published as part of a collection of papers that focused on the links between climate change and extreme weather events.

“Nobody’s saying this event (California’s drought) was caused by climate change, period,” said Daniel Swain, a grad student at Stanford and lead author of the paper. (He also coined the term “ridiculously resilient ridge.”) “The question that is being asked — and really can be asked — is, ‘Has the risk of an event like this changed due to climate change?’”

The answer, he says, is yes. It’s three times more likely, according to computer models, than if humans weren’t releasing greenhouse gases into the atmosphere. Swain said there are a number of things that can cause high pressure regions; often they’re tied to the oceans, but he wasn’t looking at the ultimate cause, just at the likelihood.

That approach has limitations, said Bill Patzert, a climatologist at NASA’s Jet Propulsion Lab. “The state of the art projections by many of these climate models, we have to remember they’re experimental. They’re getting better and better, but at this point, you definitely don’t want to invest your 401(k) in any of these climate models because many of them are in their infancy.”

Swain’s study was published as part of a collection focused on the links between climate change and extreme weather events. Two of the other studies also examined the California drought. One found that fewer Pacific storms are likely to reach California, but that increased humidity means that the ones that do reach California will be wetter. The other examined if increases in sea surface temperatures caused by global warming are responsible for the California drought. It did not find a link between the two.

With regard to climate model research, Patzert said he’s worried that it misses what he says are more immediate concerns: development and population.

“Global warming is the real deal. It’s serious, it’s irreversible and it’s going to be punishing as we look out into the 21st century,” he said. But  “the model doesn’t tell you that you’re using too much water in your yard and that farmers are growing too much almonds and too much rice. It doesn’t tell you that, but those are the real issues in the next two decades, not global warming. These reports never deal with that, and that’s the human factor and the population factor.”

The Connection Between California’s Drought and Climate Change 30 September,2014Molly Samuel

  • DavidsComments

    Patzert is completely correct when he points out that uninhibited development in the state without taking into consideration the water budget for the developed areas is the greatest driver for the water shortage. But this has nothing to do with Swain’s study, which is what this news item is about. Swain connects the increase in atmospheric CO2 to the increase in ocean temperatures to the probability of the high pressure ridge that diverts storms from California. The conclusion of his team’s study is that the high pressure ridge is much more likely to form and to remain in place for extended periods now that the Western Pacific has warmed so dramatically.

    I encourage everyone to visit his blog at weatherwest.com, where you can read a layman’s version of this study along with previous discussions of the Ridiculously Resilient Ridge.


Molly Samuel

Molly Samuel joined KQED as an intern in 2007, and since then has worked here as a reporter, producer, director and blogger. Before becoming KQED Science’s Multimedia Producer, she was a producer for Climate Watch. Molly has also reported for NPR, KALW and High Country News, and has produced audio stories for The Encyclopedia of Life and the Oakland Museum of California. She was a fellow with the Middlebury Fellowships in Environmental Journalism and a journalist-in-residence at the National Evolutionary Synthesis Center. Molly has a degree in Ancient Greek from Oberlin College and is a co-founder of the record label True Panther Sounds.

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