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Monday, December 5, 2016

On Tuesday, Stanford scientists released a study showing that the drought devastating California is indirectly caused by manmade climate change.

In the Bulletin of the American Meteorological Society, Professor Noah Diffenbaugh, graduate student Daniel Swain, and their colleagues used computer simulations and statistical analyses to examine the persistent region of high atmospheric pressure over the Pacific Ocean. The study was able to determine that this region, or “ridge,” as scientists have begun referring to it, was more likely to form in the presence of modern greenhouse gas concentrations than ever before.

Diffenbaugh and Swain have studied the ridge — or, as Swain calls it, the “Ridiculously Resilient Ridge” (Triple R) — over the course of the long-lasting drought. The Triple R is a large, hard bubble of high-pressure air that has situated itself over the Pacific Ocean. Its presence has disrupted the usual wind patterns in the area.

The Triple R subsided for a couple of months during summer 2013, but it was back by the fall. It remained in place through most of winter 2013, which is usually California’s wet season.

By January 2014, the Triple R was a force to be reckoned with. It spread from the subtropical Pacific near Hawaii to the coast of the Arctic Ocean north of Alaska, and effectively prevented California from receiving its usual complement of winter storms and precipitation. The snow and rain that would have fallen on the West Coast was instead redirected toward Alaska and the Arctic Circle.

There was no doubt in the scientists’ minds that the Triple R was affecting California’s drought. The question was whether manmade climate change influenced the creation of such a resilient ridge. In their study, Diffenbaugh and his colleagues focused on the probability of extreme ridging events. The findings were published as part of the collection “Explaining Extreme Events of 2013 from a Climate Perspective.”

The researchers found that the immensity and constancy of the Triple R in 2013 were unmatched by any previous event. As the National Science Foundation reports, the group “found that the extreme heights of the Triple R in 2013 were at least three times as likely to occur in the present climate as in the preindustrial climate.”

The scientists acknowledge that a number of factors can cause high-pressure regions and ridges, but the study wasn’t looking at the ultimate cause, just at the likelihood.

While the projections made by the climate models are experimental, they are improving in accuracy. NPR‘s science blog KQED Science quoted Bill Patzert, an expert from NASA’s Jet Propulsion Lab, on his view of climate models: “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.”

Patzer warns against expecting climate models to be 100 percent accurate, but he also states that “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.”

Let’s hope that a few more than just 3 percent of Republicans in Congress hear his plea to take global warming seriously.

Photo via Wikimedia Commons

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