California flooding on such a winter's day

Can Californians blame climate change for their latest weather woes?

Maybe.

Heavy rains hammered Northern California and Nevada over the weekend, causing floods, power outages, and hundreds of evacuations. The storms, which could continue through Thursday, are caused by atmospheric rivers (bands of moisture in the sky) flowing from the Pacific Ocean to the West Coast.

Atmospheric river storms are nothing new. The West Coast gets 30 to 50 percent of its annual rainfall from these flows. But California’s atmospheric river storms will get more frequent, stronger, and more destructive as the climate warms. Whether that’s already happening is unclear.

“It’s tough to point at a given storm and say oh this is climate change,” hydrologist Michael Dettinger of the U.S. Geological Survey told Grist. “I don’t have the tools to tell you that in this case, climate change increased the odds of [California’s storms] by X amount,” he says. “But I can tell you that this is what climate change looks like.”

In the future, the West Coast can expect to see prolonged droughts punctuated by huge storms, he says. Strong droughts and floods are expected to increase at least 50 percent in California toward the end of this century.