DENVER (AP) — River basins around the world that were once regularly covered in snow are increasingly seeing their snowpack shrink and climate change is to blame, a new study shows.
“Many of the world’s most densely populated basins are on the brink of rapid snowfall,” concluded the study of snow amounts since 1981 in the Wednesday journal Nature.
That’s because the study found a key threshold for the future of snowpacks in the Northern Hemisphere: 17.6 degrees (-8 degrees Celsius). In places where the winter temperature is colder on average, the snow pack often survives because it is cold enough. But areas warmer than 17.6 degrees for a winter average tend to see their winter wonderland dreams melt away like the Wicked Witch of the West. And it happens quickly.
“You may be in this regime of very rapid and accelerating losses due to warming,” said lead author Alexander Gottlieb, an Earth system scientist at Dartmouth College.
Most previous studies have looked at snow cover, which is a simple measurement of whether there is snow on the ground or not. This latest study examined snowpack, a more comprehensive measurement that includes depth and amount, at its overall peak in March. Spring snow cover is crucial for providing a steady supply of drinking and irrigation water to billions of people, with larger and earlier melts causing problems.
Earth system scientist Elizabeth Burakowski of the University of New Hampshire, who was not part of the study, said the study “demonstrates beyond a reasonable doubt that humans are responsible for the decline of snow cover in dozens of watersheds in the Northern Hemisphere” and the melting of the snow. the snow “will increase with every degree.”
“The study shows that our snow future depends on the path we take to address the climate,” Burakowski wrote in an email.
Gottlieb and Dartmouth climate scientist Justin Mankin examined 169 watersheds in the Northern Hemisphere and found a significant downward trend over 40 years in 70 of the watersheds, an increasing trend in a dozen watersheds, and no trend in the others.
In 23 of those shrinking snowpacks, Mankin and Gottlieb were able to show, using variations on standard scientific techniques, that climate change clearly contributed to the melting. In eight river basins, all in cold eastern Siberia, they found that climate change helped snowpack form as precipitation increased but temperatures remained cool enough to maintain snowpack.
Europe and North America experience some of the worst snow losses in spring, they found, including the Great Salt Lake, Merrimack, Connecticut, Susquehanna, Hudson, Delaware, Neva, Vistula, Dnieper, Don and Danube watersheds.
A good example of a shrinking snowpack is the upper Colorado River basin in Colorado and parts of Wyoming, Gottlieb said. There, winter temperatures average around 23 degrees (-5 degrees Celsius), apparently cold enough for snow because it’s below freezing, but not really, he said.
“This is a place where we’re starting to see these types of accelerating losses occur,” Gottlieb said. “We see a very clear picture of the anthropogenic loss of forest snow over the last forty years.”
Gottlieb and Mankin documented fingerprints of human-induced warming using the standard climate attribution method, comparing what’s happened over the past 40 years of a real warming world to thousands of computer models showing what’s happening to these river basins on a fictional planet would happen. no climate change.
Places colder than 17.6 degrees account for 81 percent of the Northern Hemisphere’s snow cover, but not many people live there, only 570 million, Mankin said. More than 2 billion people live in areas where winter averages are between 17.6 and 32 degrees (-8 and zero Celsius), he said.
Most importantly for water supplies, “as warming accelerates, snow cover change will accelerate much faster than it is now,” said Daniel Scott, a scientist at the University of Waterloo who was not involved in the study. was involved.
That’s because what’s happening isn’t gradual. Above a certain temperature, the melt starts moving quickly. Below that 17.6 degree limit, it is cold enough that the extra moisture in the air due to climate change could result in more snow and an increase in snowpack, something Gottlieb and Mankin said they have seen in eastern Siberia.
That 17.6-degree threshold “tells us more clearly how much risk there is and where,” said University of Colorado ice scientist Waleed Abdalati, a former NASA chief scientist who was not part of the study.
The ski industry — with sometimes stark images of manufactured snow on an otherwise brown landscape for winter enthusiasts to enjoy — has long been an easy-to-understand example of an economy that will suffer from the lack of snow.
Many ski areas wait anxiously every year for Mother Nature to bring enough powder to operate their lifts. Others have closed altogether after their seasons became too short.
Larger corporate-run mountains, such as Colorado’s Aspen Snowmass, can operate consistently despite less snow and shorter winters.
“Opening and closing days remain constant due to snowmaking, which shows how important that is,” said Auden Schendler, senior vice president of sustainability at Aspen One, the parent company of Aspen Skiing Company.
They also invested in building new ski slopes at higher altitudes, where snow is more reliable than at the base, protecting them – for now – from substantial economic losses.
“That in no way reduces the urgency of the need to act with force and on a large scale,” Schendler said. Aspen Snowmass is among a growing handful of ski resorts that are embracing climate activism as the new industry standard, recognizing the urgent need to lobby for climate-friendly policies if they want to survive well into a warming future.
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Peterson reported from Denver, Borenstein from Kensington, Maryland.
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