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Human-driven climate change is to blame for sharp snowpack declines since 1980

Snow, a seemingly simple yet perplexing aspect of our climate, has recently been at the forefront of discussions on global warming. The fluctuating patterns of snowfall and snowpack across the globe have raised crucial questions about climate change and the future of our planet.

Winter seasons in recent years have been marked by contrasting snow patterns. Regions from Oregon to New Hampshire witnessed a notable lack of snowfall in December, painting a stark picture of a warming world.

The landscapes, more brown than white, and the severe snow drought in the American Southwest, seemed to signal a dire future.

In stark contrast, record blizzards like those seen in early 2023 have challenged our understanding. These blizzards, which buried California mountain communities, replenished dry reservoirs, and dropped an astonishing 11 feet of snow in northern Arizona, appeared to contradict the narrative of a warming planet.

Scientific climate change data on snowpack

The confusion extends to scientific data as well. Ground observations, satellite data, and climate models have shown inconsistent results regarding the impact of global warming on snowpacks in high-elevation mountains.

This inconsistency complicates efforts to manage potential water scarcity for many population centers.

Addressing these uncertainties, a recent study from Dartmouth provides valuable clarity. The research confirms that seasonal snowpacks across the Northern Hemisphere have significantly diminished over the past 40 years.

This decline, attributed to human-driven climate change, is most pronounced in certain regions. The Southwestern and Northeastern United States, along with Central and Eastern Europe, have seen snowpack reductions ranging from 10% to 20% per decade.

Implications for global populations

This loss of snowpack has dire implications for hundreds of millions of people in North America, Europe, and Asia who rely on snow for their water supply.

As first author Alexander Gottlieb, a PhD student at Dartmouth, points out, “The most immediate and potent risk that climate change poses to society is the loss of the water reservoir stored in snow.”

Gottlieb emphasizes that the study identifies watersheds that have historically lost snow and those most vulnerable to future declines.

He warns of regions like the Southwestern and Northeastern United States approaching near snow-free conditions by the end of March by the end of the 21st century, highlighting the urgency of adapting to water scarcity.

“Our work identifies the watersheds that have experienced historical snow loss and those that will be most vulnerable to rapid snowpack declines with further warming,” Gottlieb said.

“The train has left the station for regions such as the Southwestern and Northeastern United States. By the end of the 21st century, we expect these places to be close to snow-free by the end of March. We’re on that path and not particularly well adapted when it comes to water scarcity.”

Impact of snowpack decline from climate change

However, the implications of snow loss extend beyond water security. Justin Mankin, an associate professor of geography and the paper’s senior author, sheds light on the economic repercussions.

Regions like the Northeastern U.S., facing steep declines in snowpack, are at risk of significant economic losses, particularly in states reliant on winter recreation.

Vermont, New York, and New Hampshire, for example, could see their economies suffer as even machine-made snow becomes less feasible due to rising temperatures.

Mankin further highlights the disproportionate impact on vulnerable communities. Lower elevation ski resorts, already grappling with decreasing snow, face accelerated challenges.

Continuation of the trend could lead to the consolidation of skiing activities into larger, more resourced resorts. This shift could have far-reaching consequences on local economies and cultural values.

Decoding snowpack changes with AI

In a world grappling with the effects of global warming, understanding the dynamics of snowpacks is crucial. Gottlieb and Mankin’s study, spanning from 1981 to 2020, delved into the changes in snowpack across 169 river basins in the Northern Hemisphere.

Their focus was on how global warming’s influence on temperature and precipitation patterns has transformed these snowpacks. The loss of snowpacks means potentially less meltwater in spring, affecting rivers, streams, soils, ecosystems, and, importantly, people’s access to water.

The researchers employed a machine learning model to analyze a vast array of data. They examined thousands of observations and climate-model experiments, which included snowpack, temperature, precipitation, and runoff data.

This innovative approach allowed them to pinpoint where and how warming has led to snowpack losses. Crucially, it also enabled them to study the complex interplay between temperature and precipitation changes — factors that decrease and increase snowpack thickness, respectively.

A key achievement of their study was identifying uncertainties in both models and observations. This understanding allowed them to discover aspects previously overlooked in assessing climate change’s impact on snow.

Their methodology builds upon a 2021 study by the same researchers, which improved predictions of water availability by leveraging uncertainties in measuring snow depth and defining snow drought.

Challenging common misconceptions about snow

Mankin highlights the complexities surrounding snow measurements and their implications for water security. “Snow observations are tricky at the regional scales most relevant for assessing water security,” he said.

“Snow is very sensitive to within-winter variations in temperature and precipitation, and the risks from snow loss are not the same in New England as in the Southwest, or for a village in the Alps as in high-mountain Asia,” Mankin continued.

The study reveals a striking dichotomy. About 80% of the Northern Hemisphere’s snowpacks, predominantly in far-northern and high-elevation areas, experienced minimal losses or even expansion in places like Alaska, Canada, and Central Asia. This expansion is attributed to increased precipitation in these colder regions.

Conversely, the remaining 20% of snowpacks, crucial for many major population centers, have seen significant reductions. Since 1981, these snowpack declines have been largely inconsistent due to observational uncertainties and natural climate change variations.

However, Gottlieb and Mankin observed a consistent annual pattern of snow accumulation decline, leaving these regions increasingly short of new water supplies from snowmelt.

The “Snow-Loss Cliff” and its implications

One of the study’s most alarming findings is the identification of a “snow-loss cliff.” This term refers to a critical temperature threshold (17 degrees Fahrenheit or minus 8 degrees Celsius) beyond which snow loss accelerates, even with modest local temperature increases.

Many densely populated watersheds, reliant on snow for their water supply, face accelerated snow losses in the coming decades.

“It means that water managers who rely on snowmelt can’t wait for all the observations to agree on snow loss before they prepare for permanent changes to water supplies. By then, it’s too late,” Mankin warns.

Manking stresses the need for immediate preparation for permanent changes in water supplies, as waiting for complete observational consensus is too late. Once a watershed crosses the snow-loss threshold, the challenge becomes adapting to enduring alterations in water availability.

“Once a basin has fallen off that cliff, it’s no longer about managing a short-term emergency until the next big snow. Instead, they will be adapting to permanent changes to water availability,” he explained.

In summary, Gottlieb and Mankin’s study is a critical contribution to our understanding of the complex relationship between climate change and snowpacks. It highlights the urgent need for regions to prepare for and adapt to these changing conditions, ensuring the sustainability of water resources in a warming world.

The full study was published in the journal Nature.


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