DENVER (AP) — Snowpacks in river basins around the world that were once regularly covered in snow are shrinking, and climate change is to blame, a new study finds.
“Many of the world’s most populous basins are on the verge of rapid snow declines,” concluded the study of snow amounts since 1981 in Wednesday’s journal Nature.
That’s because the study found an important threshold for the future of snowpack in the Northern Hemisphere: 17.6 degrees (-8 degrees Celsius). In places where the average winter temperature is colder than this, snowdrifts often survive because they are cold enough. But regions with a warmer winter average of 17.6 degrees tend to see their winter wonderland dreams melt away like the wicked witch of the west. And this is happening quickly.
“Potentially, you’re in a regime of really rapid and increasing losses with warming,” said lead author Alexander Gottlieb, an Earth systems scientist at Dartmouth College.
Most past studies have looked at snow cover, which is a simple measurement of whether there is snow on the ground. This latest study examined snowpack, a more comprehensive measurement that includes depth and amount, at its overall peak in March. Spring snowdrifts are critical to providing a stable supply of drinking and irrigation water to billions of people; larger and earlier melts cause problems.
University of New Hampshire Earth systems scientist Elizabeth Burakowski, who was not part of the study, said the study shows “beyond a reasonable doubt” that humans are responsible for the decline and melting of snowpack in dozens of river basins throughout the Northern Hemisphere. snow “will increase with each degree.”
“The study shows that our snow future depends on the path we take on climate,” Burakowski wrote in an email.
Gottlieb and Dartmouth climate scientist Justin Mankin examined 169 river basins in the northern hemisphere and found a significant 40-year downward trend in 70 of the river basins, an increasing trend in a dozen, and no trend in the others.
Using variations of standard scientific techniques on 23 of the shrinking snowpacks, Mankin and Gottlieb were able to show that climate change clearly contributed to the melting. In eight river basins, all in frigid eastern Siberia, they found that climate change helped build snowpack as precipitation increased, but temperatures remained cold enough to maintain it.
Europe and North America experience some of the largest spring snowpack losses, including the Great Salt Lake, Merrimack, Connecticut, Susquehanna, Hudson, Delaware, Neva, Vistula, Dnieper, Don, and Danube river basins.
Gottlieb said a good example of shrinking snow cover would be the upper Colorado River basin in Colorado and parts of Wyoming. He said the average winter temperature there is around 23 degrees (-5 degrees Celsius), which looks like it’s cold enough to snow because it’s below freezing, but it’s actually not.
“This is a place where we’re starting to see these kinds of accelerating losses start to emerge,” Gottlieb said. “We’re seeing a really clear picture of anthropogenic forest snow loss over the last 40 years.”
Gottlieb and Mankin documented the fingerprints of human-induced warming using the standard climate attribution method, which compares what happened in the last 40 years of a real warming world with thousands of computer model runs showing what would happen to these river basins on a fictional planet. There is no climate change.
Mankin said that places colder than 17.6 degrees make up 81 percent of the Northern Hemisphere’s snow mass, but these places do not contain many people, only 570 million people. More than 2 billion people live in regions where winter temperatures average between 17.6 and 32 degrees (-8 to zero Celsius), he said.
What’s important, especially from a water supply perspective, is that “as warming accelerates, snow cover change will accelerate much faster than before,” said Daniel Scott, a scientist at the University of Waterloo who was not involved in the study.
Because what is happening is not gradual. Above a certain temperature, the melt moves rapidly. That sub-17.6-degree air is cold enough that extra moisture in the air from climate change could result in more snow and increase snow cover, as Gottlieb and Mankin say they saw in eastern Siberia.
That 17.6-degree threshold “tells us more clearly how much risk there is and where it is,” said University of Colorado ice scientist Waleed Abdalati, a former NASA chief scientist who was not part of the study.
With stark visuals of snow produced on a sometimes brown landscape for winter enthusiasts to enjoy, the ski industry has long been an easy-to-understand example of an economy that would suffer from a lack of snow.
Many ski areas anxiously wait each year for Mother Nature to bring enough powder to power their lifts. Some have closed completely because their seasons have become too short.
Larger mountains operated by companies, such as Aspen Snowmass in Colorado, are able to operate consistently despite less snow and shorter winters.
“Opening and closing days remain constant due to snowmaking, which shows how important this is,” said Auden Schendler, senior vice president of sustainability for Aspen One, parent company of Aspen Ski Company.
They have also invested in building new ski slopes at higher altitudes, where the snow is more reliable than at the base, protecting these slopes from significant economic losses for now.
“This in no way diminishes the urgency of the need to act robustly and at scale,” Schendler said. Aspen Snowmass is among a growing handful of ski areas that are embracing climate activism as the new industry standard and recognizing the urgent need to lobby for climate-friendly policies if they are to survive a warming future.
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Peterson reported from Denver, Borenstein from Kensington, Maryland.
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