Snow, often considered a paradoxical indicator of climate change, has become a focal point in understanding global warming’s intricate dance with our planet. Recent winters, marked by a dearth of December snowpack, hinted at a warming future. In a bid to demystify the uncertainties surrounding snowpack changes, a new study from Dartmouth College provides compelling evidence that seasonal snowpacks across the Northern Hemisphere have significantly diminished over the past four decades due to human-induced climate change. This research, published in the journal Nature, points to a particularly sharp decline of 10% to 20% per decade in the South-western and North-eastern United States, along with Central and Eastern Europe.
PRECIPICE OF CRISIS: THREATENING WATER SECURITY FOR MILLIONS
The study, led by Alexander Gottlieb, a PhD student at Dartmouth, and senior author Justin Mankin, raises alarms about the implications of this snowpack loss for water-dependent populations. With the most substantial reductions in regions crucial for water supply, including the South-western and North-eastern United States, the study suggests that hundreds of millions of people in North America, Europe, and Asia are on the brink of a water crisis exacerbated by continued warming.
IMMEDIATE RISK: THE VANISHING RESERVOIR OF SNOW
Gottlieb underscores the immediacy and potency of the risk posed by climate change-induced snow loss. “The loss of that reservoir is the most immediate and potent risk that climate change poses to society in terms of diminishing snowfall and accumulation,” he states. The study identifies watersheds experiencing historical snow loss and those vulnerable to rapid declines, predicting snow-free conditions in critical regions by the end of March by the close of the 21st century.
ECONOMIC AND RECREATIONAL REPERCUSSIONS
Justin Mankin expands on the multifaceted impact of snow loss, highlighting its repercussions beyond water security. Watersheds in the North-eastern U.S., such as the Hudson, Susquehanna, Delaware, Connecticut, and Merrimack, witness steep declines in snowpack, affecting economies in states like Vermont, New York, and New Hampshire. The threat extends to winter recreation, with ski resorts facing increasing challenges, potentially leading to a consolidation that disrupts local economies.
SNOWPACK LOSS PATTERNS: A DETAILED EXAMINATION
The Dartmouth study delves into the influence of global warming on temperature and precipitation, driving changes in snowpack across 169 river basins in the Northern Hemisphere from 1981 to 2020. Utilizing a machine learning model, the researchers navigate through thousands of observations and climate-model experiments, pinpointing areas experiencing snowpack losses due to warming. The counteracting effects of temperature and precipitation changes are also examined, offering a comprehensive understanding of the dynamic.
SNOW OBSERVATIONS: UNRAVELING THE COMPLEXITY
Mankin emphasizes the challenges of measuring snow’s impact on regional water security. “People assume that snow is easy to measure, that it simply declines with warming, and that its loss implies the same impacts everywhere. None of these are the case,” he explains. The study reveals that 80% of the Northern Hemisphere’s snowpacks, located in its far-northern and high-elevation reaches, have experienced minimal losses. However, the critical 20% supplying water to major population centres faces significant declines.
SNOW-LOSS CLIFF: A TIPPING POINT IN WATER SCARCITY
The study introduces the concept of a “snow-loss cliff,” signalling a critical threshold where snow loss accelerates rapidly. As average winter temperatures surpass 17 degrees Fahrenheit, even modest local temperature increases trigger accelerated snow loss. Highly populated watersheds dependent on snow for water supply find themselves teetering on this precipice, facing accelerating losses in the coming decades.
URGENCY IN ADAPTATION: A CALL FOR PROACTIVE WATER MANAGEMENT
Mankin emphasizes the urgency in adapting to permanent changes in water availability, urging water managers not to wait for unanimous observations on snow loss. “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 warns. The study serves as a clarion call for proactive measures to address the imminent and irreversible consequences of snowpack decline.
IS CLIMATE CHANGE AFFECTING SNOW?
Natural snow depth has been declining since the late 1950s because of climate change, and is projected to continue declining. Adaptation strategies being carried out include cloud seeding, conservation management and increased snowmaking for alpine ski resorts.
Climate change can affect the amount, location, and timing of snowfall, as well as the dynamics of snowmelt. These changes can vary by region. Climate change can also lead to changes in the type of precipitation. For example, more winter precipitation may fall as rain instead of snow. Snow and ice can easily change between solid and liquid states in response to relatively minor changes in temperature. Snow can occur at very low temperatures, but most heavy snowfalls occur when the air near the ground is relatively warm.