Climate crisis is reducing snow accumulation, study says – 01/10/2024 – Environment

Changes in snowfall patterns have far-reaching consequences, ranging from water shortages to the closure of ski resorts. A new study confirms that human-caused climate change has affected snow patterns across the Northern Hemisphere, including clear declines in snowpack in at least 31 watersheds.

Additionally, researchers found that when a region warms to an average temperature of -8°C throughout the winter, it appears to reach a tipping point where snow begins to melt rapidly.

“After this value, things get completely out of control,” said Justin Mankin, a geography professor at Dartmouth College and co-author of the study, which was published this Wednesday (10) in the journal Nature.

Declines in snowpack — the total mass of snow on the ground — have serious implications for places that depend on spring snowmelt as a source of water.

Major storms across the United States this week deposited a lot of snow, but the snow now on the ground may not last until the end of winter. In the short term, climate change could create deeper snowpack due to blizzards driven by increased precipitation, but with warmer temperatures, this snow will likely melt faster and may not remain on the ground.

The researchers studied data from more than 160 river basins to analyze how much snow remained in March (at the end of winter in the Northern Hemisphere) each year from 1981 to 2020. In about 20% of these areas, they found clear declines in snow accumulation. snow that could be attributed to human-caused climate change.

The Northeast and Southwest United States are among the regions with the biggest drop in snowpack, along with much of Europe.

These changes have not been uniform or linear across the world. Even as temperatures rise, places that were already colder may not rise above the freezing point of water (0°C) enough during the winter to lose much snow accumulation.

But once an area reaches a winter average of -8°C, losses accelerate exponentially.

“Every degree of warming beyond that threshold is doing more harm,” said Alexander Gottlieb, a doctoral student in Mankin’s group and lead author of the study.

In much of the Western United States, snowpack has historically acted as a frozen reservoir, which stores water during the winter and releases it in the spring and summer when demand is greatest. When snow does not accumulate during the winter, droughts during the summer can be exacerbated.

In the Northeast, snow is less important for water supplies, but it is the basis for winter recreation, tourism and culture.

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

The researchers also modeled snow accumulation in a hypothetical world without climate change, over the same period, to see if taking global warming out of the equation would produce significantly different results. This happened in 31 of the river basins studied, or about 20% of the total, meaning the influence of climate change is clear in these places.

“There are some watersheds where we see this very clear signal,” Gottlieb said. In general, these watersheds have warmed beyond the -8°C tipping point identified by the researchers. Because humans tend to live in places with milder climates, these warmer regions are those with the largest populations.

“With additional warming, you’re going to have more and more of these highly populated watersheds pushed beyond that limit,” Gottlieb added.

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

Young examined the effects of climate change on snow cover, a measure of whether or not there is snow on the ground, regardless of depth. Unlike snow accumulation, snow cover can be reliably measured by satellites. Global snow cover has declined by about 5% annually from 2000 to 2023, according to a separate study published by Young last year.

While studying snow accumulation is useful in revealing potential consequences for water supplies, studying snow cover illuminates another problem: White snow reflects sunlight back into the atmosphere, while exposed dark soil absorbs sunlight. . Therefore, once snowpack drops to the point where there is no longer any snow on the ground, a feedback loop warms the planet further.

“This becomes another way our world is warming,” Young said.