Four decades of satellite data are revealing a clear shift in how, where and when snow falls across the Northern Hemisphere, and these changes are having real impacts for millions of people, including here in the United States.
A new study published in the American Meteorological SocietyJournal of Meteorologyshows that areas losing snow cover now significantly outnumber those gaining it. In fact, regions with declining snowpack outpace those seeing increases by about 2.5-to-1, based on 43 years of observations.
The steepest declines in snow cover are being observed across Europe and much of Central Asia, where warming temperatures are shortening the winter season. In contrast, parts of central Canada and even the northern Great Plains of the U.S. are trending toward slightly more snow. That's because a warmer atmosphere can hold more moisture, and when those warmer temperatures are cold enough, that extra moisture can fall as snow.
Where The Snow Is And Isn't Across The US
Snow cover across Europe consistently shrank throughout the 40-year study period. Researchers believe this is in direct correlation with the steady rise in temperatures over that area during recent decades.
The study specified how southern Europe, as well as central Asia, is seeing earlier snowmelt, without compensation for earlier fall snow. Therefore, the snow season is simply getting shorter.
However, the study shows that one of the biggest winners when it comes to snowfall over the last four decades has been across the Northern Plains of the U.S. and parts of Canada.
Just this season alone, the U.S. has experienced a few big snowstorms across the northern tier.
Marquette, Michigan, for example, is more than 93 inches above average for snowfall this season. Part of their snow surplus was thanks toWinter Storm Iona, which dumped more than 36 inches of snow in the area. But even without the help of Iona, they would still be having a blockbuster year for snowfall.
And just before Iona,Winter Storm Hernandodumped as much as 3 feet of snow across parts of the Northeast.
While back-to-back storms clobbered the North and East, the West has been largely left out of winter. Much warmer than average temperatures and dry conditions have resulted in parts of the Colorado snowpack being at record lows.
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These snowy versus snowless trends we're seeing this year are in line with the longer-term research trends. Snow trends are shifting, creating big impacts worldwide.
Climate Is Changing The Seasons
The bigger shift may not be about how much snow falls, but more about when it arrives, and how quickly it disappears.
The study shows that snow seasons are beginning a bit earlier in the fall in some locations, but melting significantly sooner in the spring. That earlier snowmelt is especially important for the western U.S., where mountain snowpack acts as a natural reservoir.
When snow melts too soon, that water runs off earlier in the year, leaving less available during the hot summer months when demand is highest. This can increase the risk of water shortages, strain agriculture and heighten wildfire danger.
This season's snowpack in parts of Colorado is at record lows due to several heat waves and dry conditions that have left much of the state well below average for snowfall this season.
Snowfall also acts as a natural "air conditioner" for our planet. The snow helps reflect the sun's heat, keeping our planet cooler. However, when there's no snow, the Earth absorbs that heat, adding to additional warming.
The area where the snowfall is arriving sooner and melting sooner trend was most pronounced was in the Arctic. Researchers saw snow disappearing earlier and earlier during each decade that was studied. This is putting the Arctic very close to the threshold where permafrost begins melting and releasing vast amounts of carbon and methane.
For everyday Americans, these changes are already showing up in various ways: shorter ski seasons in some regions, shifts in spring flooding patterns, and drier conditions later in summer.
While year-to-year snowfall will always vary, this research shows long-term trends are pointing to not only less snow across the Northern Hemisphere, but a shifting winter climate. And that shift will likely play a growing role in water resources, ecosystems and seasonal weather patterns in the years ahead.
Jennifer Grayis a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.
