Play Live Radio
Next Up:
0:00
0:00
0:00 0:00
Available On Air Stations

California Could See Longer Summers, Wetter Winter Storms By Century’s End

CSU Chico

California’s future is bright. Too bright. 

A paper published in the journal Science Advances predicts longer, hotter and drier summers by the end of the century, along with wetter and warmer winter storms due to rising concentrations of carbon dioxide and other greenhouse gasses in the atmosphere. 

Dr. Daniel Swain, a climate scientist at UCLA, the National Center for Atmospheric Research and the Nature Conservancy of California and one of the authors of the paper, says the seasonal weather swings typical of California will grow more dramatic.

“The sort of characteristics of California’s climate that we’re already used to become, if you will, more pronounced, or more extreme,” he said. 

According to the research, swings between drought and wet years will become more pronounced. Fewer ordinary storms will drift inland from the Pacific, but Atmospheric River events — big storms delivering deluges of sub-tropical moisture will grow more numerous, warmer and more intense. 

“What we’re saying, in our paper here, is that of the most intense atmospheric river storms that we see, those most extreme storms will become significantly more intense and bring a lot more water,” he said.

Overall, Swain sees these stronger A-R storms, with 20 to 30 percent more moisture, making up for the precipitation lost from fewer, weaker storms. California’s net amount of rain should be roughly the same — the devil though, is in the details.

Atmospheric rivers will grow three to five degrees warmer than today. That means more high elevation rain, and more of California’s precious winter snowpack washing into creeks and rivers too soon, leaving little to replenish reservoirs by summer. It also means changes for dam operators. 

“Essentially, the increase in run-off and flood risk during these mid-winter storm events is going to mean that to maintain adequate safety margins in these large pieces of water infrastructure, like dams, the dams can’t be as full,” Swain said.

That could upend how California manages water supplies. Swain said a possible solution would restore parts of the valleys to floodplain, enabling flood waters to percolate into the earth and refill depleted aquifers. 

Other key findings suggest downpours growing 30-50 percent heavier, increasing risk of mudslides. And that storms will also be less confined to the western slope of the Sierra; and that the valley, eastern slope and areas currently in rain-shadowed valleys could see as much as 50 percent more rain.

None of this is set in stone, Swain said, but changing course will require a global effort.

“There’s still time to turn the ship,” he said. “We can’t avoid all of the bad outcomes, but there may still be the difference between a glancing blow and hitting the iceberg head-on.”