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(Denver) – River basins around the world that once received regular snowfall are receiving less and less snow, and climate change is to blame, a new study finds.
“Many of the world’s most populated basins are floating on a cliff of rapid snowfall,” concludes a study of snowfall since 1981 in Wednesday’s Journal Nature.
That’s because the study found that the key future threshold for snow cover in the Northern Hemisphere is 17.6 degrees Celsius (-8 degrees Celsius). Where the average winter temperature is lower, it is often cold enough for snowpack to survive. But in regions where average winter temperatures exceed 17.6 degrees, dreams of a winter wonderland tend to melt away like the Wicked Witch of the West. And it’s happening fast.
“We may be in a situation where the losses associated with warming are very rapid and accelerating,” said lead author Alexander Gottlieb, an Earth system scientist at Dartmouth College.
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Most past studies have focused on snowpack, which simply measures whether there is snow on the ground. This latest study looked at more comprehensive measurements, including snow cover, depth and amount at a typical peak in March. Spring snowpack is essential for providing a reliable supply of drinking and irrigation water to billions of people, and problems arise when it melts larger and earlier.
Elizabeth Burakowski, an earth system scientist at the University of New Hampshire who was not involved in the study, said the study found that “humans are responsible for the decline in snowpack in dozens of northern hemisphere river basins” and for the Earth’s melting. It has been shown “beyond a reasonable doubt” that this is the case. The snow “will increase more and more as the weather gets warmer.”
“This study shows that the future of our snowfall depends on how we act on the climate,” Burakowski wrote in an email.
Gottlieb and Dartmouth climatologist Justin Mankin studied 169 river basins in the Northern Hemisphere, 70 of which showed significant 40-year declining trends, 12 with increasing trends, and others. It was found that no trend was observed in the basins.
Applying standard scientific methods, Mankin and Gottlieb were able to show that climate change is clearly contributing to snowmelt in 23 of the shrinking snowpacks. They found that in eight river basins, all in cold eastern Siberia, precipitation increased but temperatures remained low enough to sustain snowpack, and that climate change accelerated snowpack formation.
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In Europe and North America, the Great Salt Lake, Merrimack, Connecticut, Susquehanna, Hudson, Delaware, Neva, Vistula, Dnieper, Don, and Danube river basins were found to experience the greatest snow loss in spring. did.
Gottlieb said a good example of a shrinking snowpack is the upper Colorado River basin in Colorado and parts of Wyoming. He said the average winter temperature is about 23 degrees Celsius (minus 5 degrees Celsius), which is below freezing and looks cold enough to snow, but that’s not actually the case.
“This is where you’re starting to see these kinds of accelerated losses,” Gottlieb said. “We have a very clear picture of human-induced forest snow loss over the past 40 years or so.”
Gottlieb and Mankin use standard climate attribution to compare what has happened over the past 40 years in a real-world warming world to thousands of computer model runs showing what would happen to these river basins on a hypothetical planet. The method was used to document the signature of anthropogenic warming. There is no climate change.
Mankin said 81% of the Northern Hemisphere’s snowfall is in places colder than 17.6 degrees Celsius, but not many people live there – just 570 million people. He said more than 2 billion people live in areas where the average winter temperature ranges from 17.6 degrees Celsius to 32 degrees Celsius (-8 degrees Celsius to zero degrees Celsius).
Importantly, especially for water supplies, “as global warming accelerates, snowpack change will accelerate much faster than it has in the past,” said Daniel, a University of Waterloo scientist who was not involved in the study.・Mr. Scott stated.
That’s because what’s happening isn’t gradual. Above a certain temperature, the melt begins to move rapidly. Below that 17.6 degrees, it’s cold enough that extra moisture in the air from climate change can increase snowfall and increase snowpack, which Gottlieb and Mankin said they’ve witnessed in eastern Siberia.
The 17.6-degree threshold “gives us a clearer picture of where and how much risk there is,” said Waleed Abdalati, an ice scientist at the University of Colorado. He is a former NASA chief scientist and was not involved in the study.
The ski industry, with its stark visuals of brown landscapes and occasional patches of artificial snow for winter-goers to enjoy, has long been used as a clear example of how the economy suffers from a lack of snow.
Many ski areas wait anxiously each year for Mother Nature to bring enough powder to start operating their lifts. The season has become so short that some stores have closed completely.
Large corporate-run mountains, such as Aspen Snowmass in Colorado, are able to operate reliably despite little snow and short winters.
“Snowmaking keeps business days and business days the same, which shows how important it is,” said Auden Schendler, senior vice president of sustainability for Aspen One, parent company of Aspen Ski Company. “There is,” he said.
They have also invested in building new ski resorts at higher elevations where snow is more reliable than at the foothills, and so far they have been spared serious economic losses.
“This in no way diminishes the urgency of the need to act with force and at scale,” Schedler said. Aspen He said Snowmass recognizes the urgent need to lobby for climate-friendly policies if it wants to survive into a warmer future, and is committed to making climate change action a new industry standard. He is one of the few ski resorts that employ him.
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Peterson reported from Denver and Borenstein from Kensington, Maryland.
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