by 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 found.
“Many of the world’s most populated basins are on the brink of rapid snow decline,” the study of snowfall amounts since 1981 concluded in Wednesday’s Nature magazine.
That’s because the study found a key 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, snow cover often survives because it is cold enough. But areas with temperatures above 17.6 degrees for a winter average tend to see their winter dreams melt away like the Wicked Witch of the West. And it’s happening fast.
“We are potentially in this regime of really rapid, accelerated losses with warming,” said lead author Alexander Gottlieb, an Earth systems scientist at Dartmouth College.
Most previous studies have looked at snow cover, which is a simple measure of whether the ground has snow or not. This latest research examined snow cover, a broader measure that includes depth and amount, at its overall peak in March. Spring snowpack is critical to providing a steady supply of drinking and irrigation water to billions of people, and larger, earlier snowmelts are causing problems.
Elizabeth Burakowski, an Earth systems scientist at the University of New Hampshire who was not part of the research, said the study shows “beyond a reasonable doubt that humans are responsible for the decline in snow cover in dozens of river basins throughout the northern hemisphere” and snow melting “will increase with each degree.”
“The study shows that the future of our snow depends on the path we take to act on the climate,” Burakowski wrote in an email.
Gottlieb and Dartmouth climatologist 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.
In 23 of those shrinking snowpacks, Mankin and Gottlieb, using variations of standard scientific techniques, were able to show that climate change clearly contributed to the melt. In eight river basins, all in cold eastern Siberia, they found that climate change helped form snow cover as precipitation increased, but temperatures remained cold enough to preserve it.
They found that Europe and North America are experiencing some of the largest spring snow losses, including the Great Salt Lake, Merrimack, Connecticut, Susquehanna, Hudson, Delaware, Neva, Vistula, Dnieper, Don and Danube river basins.
A good example of reduced snowpack is the upper reaches of the Colorado River Basin in Colorado and parts of Wyoming, Gottlieb said. There, winter temperatures average about 23 degrees (-5 degrees Celsius), apparently cold enough for snow because it’s below zero, but not really, he said.
“This is a place where we’ve started to see these kinds of accelerated losses starting to emerge,” Gottlieb said. “We see this really clear picture of anthropogenic snow loss in forests over the last 40 years or so.”
Gottlieb and Mankin documented the traces of human-caused warming using the standard climate attribution method of comparing what happened in the last 40 years of an actual warming world with thousands of computer models showing what would happen to these river basins in the future. a fictional planet with no climate change.
Places with temperatures colder than 17.6 degrees account for 81 percent of the Northern Hemisphere’s snow cover, but they are not home to many people, just 570 million, Mankin said. More than 2 billion people live in areas where winter averages between 17.6 and 32 degrees (-8 and zero degrees Celsius), he said.
What’s key, especially for water supply, is that “as warming accelerates, the change in snow cover 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’s because what’s happening is not gradual. Above a certain temperature, the melt moves rapidly. Below that 17.6 degree mark, it’s cold enough that extra moisture in the air due to climate change could result in more snow and increase snowpack, something Gottlieb and Mankin said they saw in the East from 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 artificial snow on an otherwise brown landscape for winter revelers to enjoy, has long been an easy-to-understand example of an economy that will be hurt by the lack of snow.
Many ski areas anxiously wait each year for Mother Nature to bring enough powder snow to start using their lifts. Others closed completely after their seasons became too short.
Larger corporate-run mountains, like Aspen Snowmass in Colorado, can operate consistently despite having less snow and shorter winters.
“Opening and closing days remain constant due to snowmaking, which shows how important it is,” said Auden Schendler, senior vice president of sustainability for Aspen One, the parent company of Aspen Skiing Company.
They also invested in building new ski slopes at higher elevations, where the snow is more reliable than at the base, insulating them from substantial economic losses, for now.
“That in no way reduces the urgency of the need to act strongly and at scale,” Schendler said. Aspen Snowmass is among a growing handful of ski areas that are adopting climate activism as the new industry standard, recognizing an urgent need to lobby for climate-friendly policies if they want to exist in a warmer future.
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Peterson reported from Denver, Borenstein from Kensington, Maryland.
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