California's recent storms were historic. They could get much worse

California’s recent storms were historic. They could get much worse

A new study reports that human-induced climate change could make winter storms in the Western U.S. bigger and more intense.

The study, which was published in Nature Climate Change, found that the storm in early January that hit the Bay Area was 5% more intense due to warming.

The storm dumped 17.74 inches of rain on San Francisco, which is 78% of the city’s yearly rainfall total. The deluge led to deadly floods and landslides across the state, killing at least 20 people and causing widespread damage.

“Five percent doesn’t sound like a lot, except it’s five percent of a big number,” Wehner said, describing the estimate as a conservative one. “When you have these big events, you’re pushing your systems to their limits — maybe exceeding their limits.”

This happened recently when rivers overtopped their banks flooding homes and and several levees broke in response to colossal downpours.

California's recent storms were historic

The new study, conducted by researchers at the Department of Energy’s Pacific Northwest National Laboratory, found that human-induced climate change is making winter storms larger and more frequent.

The most extreme systems are expected to see the biggest increases in storm intensity. Climate scientist Michael Wehner of Lawrence Berkeley National Laboratory estimates that the storm in early January that was propelled over the Bay Area by a bomb cyclone poured about 5% more rain due to warming. These events are only expected to become more frequent as climate change continues.

“The bad gets worse,” said Wehner, who wasn’t involved with the study.

The researchers utilized extensive computer modeling to analyze decades of winter storms. Historical simulations and future projections revealed that extreme storms that deposit rain and snow on the Western states will be more sizeable and intense in a warmer climate.

“These storms in the future will be producing on average about 30% more precipitation,” said study author Ruby Leung, a climate scientist at Pacific Northwest National Laboratory.
The new study provided storm details down to a scale of about 4 miles — far more zoomed in than global climate models, which typically only get down to about 60 or 120 miles, Leung said.

The high-resolution analyses showed that the wettest future storms will see the biggest increases in intensity nearest to their centers. This means that storms will become sharper, with more rain falling in a smaller area. Such concentrated rainfall could overwhelm smaller watersheds directly in the path of a storm’s center.

“I was really excited about this paper because it’s one of the few papers that examines the spatial characteristics of extreme precipitation,” said Deepti Singh, a climate scientist at Washington State University Vancouver, who was not part of the new study.

The study found that winter storms in California are sharper than in the Pacific Northwest and Southwest. The authors attribute this to California’s steep mountains, which cause atmospheric rivers to lose moisture as they travel over the state.

“But regardless of which region, we are seeing that all regions in the western United States will experience a sharpening of storms in the future,” Leung said.

To properly design bridges, dams and other infrastructure, engineers must factor in the impact of a warming world on storm output, Leung said.

The new study’s findings agree remarkably well with an earlier study co-written by Wehner, published in June 2022. That work probed how a warmer climate would alter the rain produced by a half-dozen past Bay Area storms fueled by atmospheric rivers.

According to the 2022 study, extratropical cyclones that are linked to atmospheric rivers have the greatest increases in precipitation. An example of this is the storm in early January that featured both a bomb cyclone and an air river. Winters on the West Coast are often when these storms have the biggest effects.

“Bad news is that the (storms) that are most commonly causing damage are the ones that are most sensitive to climate change,” Wehner said.
The impacts of global warming on weather aren’t something that will happen in the distant future, Wehner said, as shown by the historic three weeks of storms that wreaked havoc on parts of Northern California and the Central Coast

“Dangerous climate change is here now.”

A new study in Nature Climate Change found that human-induced climate change could make Western U.S. winter storms bigger and more intense. The study also showed that these storms are expected to become more frequent, and infrastructure must be designed to factor in the impact of a warming world on storm output.

The wettest future storms will see the biggest increases in intensity nearest to their centers, which could overwhelm smaller watersheds directly in the path of a storm’s center.

Check out this link: “Weather Alert: The Impact Of Climate Change On Storms In The Western U.S” for more information on how these storms are expected to become more frequent and the impact it could have on infrastructure.