Warming not increasing winter moisture, yet

Two near record winters in a half-dozen years prompted researchers to take a hard look at whether those years could be attributed to warmer weather conditions.

A new paper published by a California researcher indicates that so far that isn’t happening with winter moisture in the West, yet.

The winter of 2016-17 saw more than double the average moisture fall in Minden, while 2022-23’s winter resulted in significant snowfall in the Pine Nut Mountains during a rare Tonopah Low.

Park Williams of the University of California, Los Angeles, spoke Sept. 23 as part of a virtual panel on the drought outlook for this winter.

Williams said there have been various models showing that warmer temperatures would increase the amount of ocean water taken up, which could result in larger winter storms.

However, he said his research shows that not only have cool-season daily precipitation totals not intensified over the last 75 years, but that it might take another half century before they do.

“We need to start accumulating record-breaking events for some time before we see enough to trigger the time of emergence,” he said.

Williams is the first author on the paper entitled “Anthropogenic Intensification of Cool-Season Precipitation Is Not Yet Detectible Across the Western United States.”

He said that indications of earlier increased precipitation in the West conducted in other models haven’t turned up in the real world.

Increased warming should increase evaporation from the ocean because warm air can contain more moisture than cool air.

Should a warm air mass suddenly cool, like when it climbs the Sierra Nevada, it would release that moisture in the form of precipitation.

Inspiration for the study have been a cycle of record dry and wet spells in the West.

“Recent years have well justified concern on whether we’ll see more of those in the future,” Williams said. “It should drive more severe droughts and more severe flood risks.”

During the 2023-24 water year, Minden received 9.33 inches of precipitation since Oct. 1, 2023, according to National Weather Service records, within a hundredth of an inch of the annual average of 9.34 inches.

“There has been exceptional precipitation seen over the last few years,” Williams said. “Snowpacks in the Sierra were something near 250 percent of average. I drove over Sonora Pass on July 5, 2023, and there was still a lot of snow on the ground.”