Sacramento's Hurricane Sandy

They’re really coming—storms that are bigger and more devastating than anything scientists have seen before.

Forget last month’s heavy rainstorms, which dumped almost 5 inches of rain and caused flooding, downed trees and created power outages across Sacramento. That was a warm bath compared to Northern California’s coming weather apocalypse, according to some prognosticators. As the climate continues to warm, forecasters believe superstorms like Hurricane Sandy, which ripped through the East Coast in late October, might one day threaten Sacramento.

“If you have a couple of extremes that slam together at just the right place, then yeah, we do end up with an extreme event, and it is possible we would find conditions worse than anything we’d seen before,” said Michael Anderson, who manages the state’s climate program at the California Department of Water Resources.

Anderson said the cold Pacific Ocean off of California’s coast probably couldn’t spawn a hurricane, but he thinks comparable forms of severe weather might rock Sacramento as climate change gets worse. And other scientists agree.

Roger Bales, director of the Sierra Nevada Research Institute at UC Merced, also thinks a warmer atmosphere could lead to extreme changes in the state’s seasonal patterns. Bales said that “atmospheric rivers,” which are weather patterns that are funneling tropical storms from the southwestern Pacific into Northern California, already soak the region every year with winter storms.

Those tropical fronts bring more rain and less snow for the mountains, but according to Bales, a warmer atmosphere will pack greater amounts of moisture and make things much worse.

“As you warm the temperatures globally or in California, the elevation at which you get snow goes uphill, especially in the Sierra Nevada,” he said. “As the temperature gets warmer, some of those storms are pushed above freezing.”

If that happens, rain and melting snow would tumble into the Sacramento Valley’s swollen rivers like a liquid avalanche, swamping the capital like the devastating floods of 1986 and 1997. In most worse-case scenarios, a mega deluge caused by climate change would dwarf anything wrought by storms like Hurricane Sandy or Hurricane Katrina in 2005.

So how long until Sacto’s weather gets worse? Bales thinks the shift has already started, even if it’s not noticeable in Northern California just yet.

But this may change as researchers start looking more closely at Sierra Nevada snow levels. “It’s not as clear because we may not have measuring stations in the right sensitive locations,” said Bales, “but we know the trend is already apparent across much of the western United States.”

At the same time, experts don’t know exactly how big or how bad future storms will be, or how to link individual weather events to permanent changes in the atmosphere. Most scientists say those details are still a long way off.

The good news, Anderson pointed out, is that California is trying to be prepared. In 2008, the state joined forces with the U.S. National Oceanic and Atmospheric Administration to create a spanking-new weather-observation system. The $21.5 million project, which should be completed by April 2014, will use a vast network of GPS, radar, soil instruments and wind sensors to collect information on every storm that slams into the Sacramento region.

“I think one of the benefits we’re going to get is how is the climate changing in California and what impact is that having on water supply,” said Allen White, a NOAA scientist who’s managing the project. “This network will help be able to detect those climate changes with great detail across the state.”

Anderson said the new system is already spitting out data on California’s changing weather patterns. Still, he thinks several years will pass until climatologists really understand the link between global warming and severe storms.

“This is a very new endeavor,” Anderson said. “You have to have the right metrics to actually compute the statistics. It’s fairly new ground we’re working in.”