Climate change is causing a sharp drop in snow levels, research shows

Changing snow patterns have far-reaching consequences, from water shortages to closed ski areas. A new study confirms that human-induced climate change has affected snow patterns in the Northern Hemisphere, including a marked decline in snow cover in at least 31 individual river basins.

Additionally, the researchers found that when a region warms to an average temperature of 17 degrees Fahrenheit, or minus 8 degrees Celsius, throughout the winter, it appears to reach a tipping point where the snow begins to quickly melt away.

“Beyond that threshold, we see everyone going off a cliff, so to speak,” said Justin Mankin, a professor of geography at Dartmouth College and co-author of the study. published Wednesday in Nature.

Decreases in snowpack, the total amount of snow on the ground, have serious consequences for places that rely on spring snowmelt as a water source.

Major storms across the United States dumped a lot of snow this week, but the snow on the ground now may not last all winter. In the short term, climate change from snowstorms may create deeper snow due to increased precipitation, but with warmer temperatures this snow will likely melt more quickly and may not persist as snowpack.

The researchers examined data from more than 160 watersheds to determine how much snow remained each March between 1981 and 2020. In about 20 percent of these areas, they found a marked decrease in snow cover that can be attributed to human-induced climate change. .

The northeastern and southwestern United States are among the regions losing snow the fastest, along with much of Europe.

These changes have not been uniform or linear across the world. Even if temperatures are higher, places that were colder to begin with may not exceed the freezing point of water (32 degrees Fahrenheit or 0 degrees Celsius) enough in winter to lose much snow.

But after an area reaches a winter average of 17 degrees Fahrenheit, losses increase exponentially.

“Every degree of warming beyond this cliff costs more and more,” said Alexander Gottlieb, a Ph.D. student in Dr.’s group Mankin and the study’s lead author.

In much of the American West, snowpack has historically functioned as a frozen reservoir that stores water in the winter and releases it in the spring and summer, when demand is greatest. If snow does not accumulate in winter, droughts during the summer can worsen.

In the northeast, snow is less important for water supply, but it does provide a basis for winter recreation, tourism and culture.

Mr. Gottlieb and Dr. Mankin combined existing snow cover, temperature and precipitation data to reconstruct snow cover patterns over the past 40 years. While direct measurements of snow cover are available for some places, to cover larger areas scientists must fill in the blanks with calculated estimates.

The researchers also modeled snowpack in a hypothetical world with no climate change over the same period, to see whether ignoring global warming would produce significantly different results. In 31 of the watersheds they studied, or about 20 percent of the total, that was the case, meaning the impact of climate change is clear in those places.

“There are a handful of basins where we see this very clear signal,” Mr. Gottlieb said. Overall, these river basins have warmed past the 17 degree Fahrenheit tipping point that the researchers identified. Because people tend to live in places with milder climates, these warmer regions are the areas with the largest populations.

“Continued warming will push more and more of these densely populated river basins over that edge,” Mr. Gottlieb added.

This paper was “very well researched,” said Stephen Young, a professor of geography at Salem State University, who was not involved in the study.

Dr. Young has studied the effects of climate change on snow cover, a measure of whether or not snow is on the ground regardless of depth. Unlike snow layers, snow cover can be measured reliably by satellites. Global snow cover has decreased by about 5 percent annually between 2000 and 2023. according to a separate study published last year by Dr. Young.

While studying snowpack is useful for revealing potential impacts on water supplies, studying snow cover reveals another problem: white snow reflects sunlight back into the atmosphere, while dark, exposed ground absorbs sunlight. So once snow cover decreases to the point where there is no snow cover on the ground at all, a feedback loop warms the planet even more.

“It’s going to be another way that our world is warming,” said Dr. Young.