This story initially appeared on Grist and is a part of the Climate Desk collaboration.

California isn’t any stranger to large swings between moist and dry climate. The “atmospheric river” storms which have battered the state this winter are a part of a system that has lengthy interrupted durations of drought with large bursts of rain—certainly, they supply someplace between 30 and 50 p.c of all precipitation on the West Coast. 

The parade of storms that has struck California in latest months has dropped greater than 30 trillion gallons of water on the state, refilling reservoirs that had sat empty for years and burying mountain cities in snow.

But local weather change is making these storms a lot wetter and extra intense, ratcheting up the chance of potential flooding in California and different states alongside the West Coast. That’s not solely as a result of the air over the Pacific will maintain extra moisture as sea temperatures rise, main to massive rain and snow volumes, but additionally as a result of warming temperatures on land will trigger extra precipitation to fall as rain sooner or later, which can result in extra harmful floods.

The household of storms that descended on the state this week solely underscored this hazard, shattering snow records and overtopping levees throughout the state.

“There’s a cascading chain of impacts,” stated Tom Corringham, a researcher on the Scripps Institution of Oceanography at UC San Diego. “As you push the rivers harder, as you push the flood protection system harder and harder, you get sort of exponentially increasing impacts. You flood the whole floodplain, or a levee breaks, and that’s where you get the really catastrophic events.”

An “atmospheric river” is a protracted, slim ribbon of moisture that carries water vapor from the tropics to land at greater latitudes. One of essentially the most well-known examples is the “Pineapple Express,” which streams eastward from Hawaii throughout the Pacific Ocean and makes landfall on the West Coast. The time period atmospheric river originated again within the Nineties, and it caught on due to the excessive quantity of water that these ribbons can include: A single one can transfer more than twice as much water via the sky as flows out of the mouth of the Amazon, the world’s largest river by quantity.

As sea and air temperatures within the Pacific Ocean rise, the storms hitting the West Coast now retain more moisture, resulting in longer and more intense bouts of rain. At the identical time, precipitation from low- and medium-intensity storms has began to taper off, leaving California to swing on a pendulum between excessive drought and excessive rain. Research means that with additional warming, atmospheric river occasions will account for an ever bigger share of California’s whole water funds, dumping water quicker than the state can take up it.

“Across the globe, some places are gonna get wetter, and some places are gonna get drier, and for California, it looks like we’re gonna get both,” stated Corringham. “There’ll be longer periods of drought, and then when the rains come, those events are going to be more intense. For water management, that’s not what you want.”