by DENVER (AP) – River basins around the world that were once regularly covered in snow are reducing their snowpack and climate change is to blame, a new study has found.
“Many of the world’s most populous basins are suffering from rapid snow loss,” concluded the 1981 study of snow amounts in Wednesday’s journal Nature.
That’s because the study found a key threshold for future snowpack in the Northern Hemisphere: 17.6 degrees (-8 degrees Celsius). In places where the average winter temperature is colder than that, the snowpack often survives because it is cold enough. But areas warmer than 17.6 degrees in midwinter usually see their winter wonderland dreams melt away like the ugly witch of the west. And it’s happening fast.
“You could be in this regime of rapid loss and acceleration with warming,” said lead author Alexander Gottlieb, an Earth system scientist at Dartmouth College.
Most studies in the past have looked at snow cover, which is a simple measure of whether or not there is snow on the ground. This latest research examined snowpack, a more comprehensive measure that includes depth and size, at the general peak in March. Spring snowpack is critical to providing a steady supply of drinking and irrigation water to billions of people, with more and earlier melting causing problems.
University of New Hampshire Earth systems scientist Elizabeth Burakowski, who was not part of the research, said the study “shows beyond a reasonable doubt that humans are responsible for the decline in snowpack in many basins across the Northern Hemisphere ” and from the melting of the basins. the snow will “rise up with every step.”
“The study shows that our snow future depends on how we act on the climate,” Burakowski wrote in an email.
Gottlieb and Dartmouth climate scientist Justin Mankin examined 169 river basins in the northern hemisphere, finding a significant 40-year downward trend in 70 basins, an increasing trend in a dozen and no trend in the others.
In 23 of the shrinking snowpacks, Mankin and Gottlieb, using variations on standard scientific techniques, were able to show that climate change clearly contributed to the melting. In eight river basins, all in cold eastern Siberia, they found that climate change helped build snowpack as precipitation increased but temperatures remained cool enough to preserve it.
Europe and North America are receiving some of the biggest spring snowpack losses, they found, including the Great Salt Lake, Merrimack, Connecticut, Susquehanna, Hudson, Delaware, Neva, Vistula, Dnieper, Don and Danube river basins .
A good example of shrinking snowpack is the upper reaches of the Colorado watershed in Colorado and parts of Wyoming, Gottlieb said. The average winter temperature there is about 23 degrees (-5 degrees Celsius), it seems cold enough for snow because it is below freezing, but not really, he said.
“This is a place where we started to see these types of accelerated losses occur,” Gottlieb said. “We see this really clear picture of anthropogenic forest snow loss over the last 40 years or so.”
Gottlieb and Mankin documented a fingerprint of human-caused warming by using the standard climate attribution method to compare what has happened over the past 40 years of real global warming with thousands of computer model runs that show what would happen to these basins on a fictional planet with no climate change.
Places colder than 17.6 degrees up 81 percent of the Northern Hemisphere snowpack, but they are not held by many people, only 570 million, Mankin said. More than 2 billion people live in areas where the average winter is between 17.6 and 32 degrees (-8 and zero Celsius), he said.
The most important thing, especially when it comes to water supply, is that “as warming accelerates, the change in snowpack will accelerate much faster than it has,” said Daniel Scott, a scientist at the University of Waterloo who was not involved in the study.
That is because what is happening is not gradual. Above a certain temperature, melting becomes rapidly moving. Below that 17.6 degree mark, it’s cold enough that the extra moisture in the air from climate change could lead to more snow and the snowpack to rise, which Gottlieb and Mankin said they saw 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 views of manufactured snow on an otherwise brown landscape – is an easy example of an economy that will suffer from the lack of snow.
Many ski areas wait anxiously each year for Mother Nature to provide enough powder to start running their lifts. Others have been closed entirely after becoming too short.
Larger corporate-run mountains, such as Aspen Snowmass Colorado, are able to operate consistently despite less snow and shorter winters.
“Open and closed days remain constant because of snowmaking, which shows how important that is,” said Auden Schendler, senior vice president of sustainability at Aspen One, Aspen Skiing Company’s parent company.
They also invested in building new ski runs at higher elevations where snow is more reliable than at the base, insulating them from significant economic loss — for now.
“That in no way diminishes the urgency of the need to act with force and scale,” Schendler said. Aspen is among a growing number of ski areas that are embracing climate activism as the new industry standard, recognizing that lobbying for climate-friendly policies is essential if they are to exist. well into the future of heating.
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Peterson reported from Denver, Borenstein from Kensington, Maryland.
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