The natural variability of California's precipitation will become more extreme as climate change progresses, according to a new study.

Dry summers and wet winters are already a feature of California's vaunted Mediterranean climate. The frequency of very dry summers and very wet winters is expected to increase, leading to "precipitation whiplash," according to the study, published yesterday in Nature Climate Change.

"The rising risk of historically unprecedented precipitation extremes will seriously test California's existing water storage, distribution, and flood protection infrastructure," co-author and UCLA climate scientist Daniel Swain wrote in a blog post.

The study's analysis of historical precipitation records and models of future climate scenarios suggests water managers will increasingly have to grapple with drought and storms like the ones that contributed to last year's failure of the primary spillway at Oroville Dam in Northern California.

By 2100, all of California is expected to have more frequent wet seasons. A record-breaking winter like 2016 to 2017 is going to be 100 to 200 percent more likely. But flooding and other events that overwhelm the state's infrastructure are actually more granular — they occur during persistent storm sequences within seasons. So the researchers drilled down into 40-day precipitation records to see how frequent extreme storm sequences might get.

They found a 300 to 400 percent increase in the frequency of storms like those in the winter of 1861 to 1862, which saw more than 40 consecutive days of rain and the temporary relocation of the state capital from Sacramento to San Francisco due to flooding.

"In practical terms, this means that what is today considered to be the '200-year flood' — an event that would overwhelm the vast majority of California's flood defenses and water infrastructure — will become the '40-50 year flood' in the coming decades," Swain wrote.

The researchers also found a smaller expected increase, of 50 to 150 percent, in the frequency of very dry individual winters, particularly in Southern California. For extreme, multiyear dry periods, though, on the scale of the drought from 2013 to 2015, they found no significant increases except in the southernmost part of the state, due to the increased frequency of storms. "21st century droughts in California will have a greater propensity to be interrupted by brief but very wet interludes," Swain explained.

When combined, the changes on both wet and dry ends add up to a 25 to 100 percent increase in extreme dry-to-wet events.

"Such hydrological cycle intensification would seriously challenge California's existing water storage, conveyance and flood control infrastructure," the paper says.

Swain said dam managers will struggle to manage inflows and outflows as storms get more intense, as Oroville has shown. "From the climate perspective, more big dams might be a real maladaptation," he said. But establishing floodplains near cities, like the Yolo Bypass near Sacramento, can help to buffer urban areas. "We do have an example of a system in place already in California that can actually work really well in this future whiplashy climate," he said.