From Inside Climate News (Bob Berwyn):
Mountain snowpack is shrinking and melting earlier in the spring. Warmer and longer summers dry out vegetation and increase the threat of wildfires in western mountain forests, where the fire season has lengthened by at least a month since 1979.
The growing wildfire risk is just part of an accelerating cycle of global warming impacts in the world’s mountain regions, according to a new Intergovernmental Panel on Climate Change report that includes a section focused on mountains for the first time in more than 20 years.
“Snow cover duration has declined in nearly all regions, especially at lower elevations, on average by five days per decade,” the mountain chapter of the IPCC report says. On average across Western North America, the European Alps and High Mountain Asia, temperatures are warming by 0.54 degrees Fahrenheit per decade.
That’s melting glaciers and changing mountain river flows, disrupting plants and wildlife, and increasing the risk of extreme rockslides, avalanches and mountain floods caused by rain falling on snow.
Taken together, global warming impacts represent an existential threat to millions of people in the Andes, the Himalaya, the European Alps, and the U.S. Mountain West including Alaska, said Heidi Steltzer, a biologist at Fort Lewis College in Durango, Colorado, and a lead author of the mountain chapter.
Will Water Reliability Break Down?
In Crested Butte, about 100 miles southwest of Leadville, hydrologist and physicist Rosemary Carroll studies how disruptions to the water cycle will affect local ranchers and ski areas, as well as drinking and agricultural water supplies hundreds of miles away.
The IPCC assessment found that global warming will change the timing and amount of runoff, “affecting water storage and delivery infrastructure around the world,” a finding backed by research focusing on the West.
A 2016 study in six Western mountain ranges showed rising temperatures will shift the snow accumulation zone and runoff timing enough to have significant impacts on water cycles. And some towns in the Rockies and Sierra Nevada are at risk from dangerous flash floods as global warming brings rain, rather than snow, to some mountain regions.
Carroll pointed out her living room window to a craggy ridgeline where she measures how water from melted snow trickles through rocks and meadows down to the East River, on to the Gunnison River and finally into the mighty Colorado.
“The new normal is that the snowpack is melting earlier and we have earlier runoff, and that’s a fact. There’s going to be less water for a given snowpack,” she said. Even in average snowfall years, global warming is reducing the amount of available water for irrigation and storage, she said.
Her research for the University of Nevada’s Desert Research Institute and the U.S. Department of Energy will help communities adapt as global warming disrupts flows from mountain streams. Around Crested Butte, the ski industry and local ranchers will feel the changes first.
But addressing those impacts isn’t as easy as just throwing a new report on the table. Translating science into action requires working with stakeholders from the start.
“Ranchers know what’s happening, they know that things are shifting, but they’re afraid the policy will shift in a way that they will carry the burden of the change. Since they have most of the water, they fear they will have to give up the most, and that it won’t be equitable,” she said.
The states that get their water from the Colorado River are already restructuring water-sharing agreements to stave off shortages and trying to develop new storage plans to account for extreme wet and dry years.