All of the seasons in New Hampshire are warming as a result of climate change, but none as rapidly and dramatically as winter, climate scientists have found.
Those seasonal changes, and the loss of winter, threaten to significantly alter the culture and economy of the state, warn the authors of a new study, which finds that New England is warming faster than the global average. But that doesn’t mean New England is heating up faster than other inhabited regions of the world, said UNH climate scientist Elizabeth Burakowski.
While warming in the region is outpacing the global average, that could be said of nearly anywhere people live, Burakowski said, since land temperatures are rising faster than ocean temperatures. The global average is lower, in part, because oceans — which make up 70 percent of the Earth’s surface — take longer to warm, bringing average global temperatures down.
Still, the paper provides an important update on how fast temperatures in the region are warming in different seasons and it uses the best temperature data available to do so, said Erich Osterberg, a Dartmouth climate scientist. Osterberg said the findings are consistent with trends that have been evident over the past few decades.
“The winter warming is truly astonishing,” Osterberg said.
The study finds that since 1900 the average annual temperature in New Hampshire increased by 1.73 degrees Celsius, already surpassing the 1.5-degree cap established in the Paris Climate Accord, a goal that almost 200 countries agreed to in 2015, in order to avoid the worst impacts of climate change. And the New Hampshire winter has warmed even more, with the average winter temperature climbing 2.50 degrees Celsius in that same timeframe.
For climate scientists, these numbers underscore how winter is receding.
“We’re losing the cold, snowy winter which defines this place culturally, economically, in terms of tourism,” Osterberg said. “It’s what a lot of us love about living here: our winters. It’s more than changes to the climate; it’s changes to our livelihood and our culture.”
Warming winters and diminished snow cover are already being felt by skiers and ski resorts — as well as maple syrup producers — as scientists continue studying how the changing climate impacts the ecosystem.
“Winter is the fastest changing season in our region, and for those of us in New England, that may be one of the most tangible and visible impacts of climate change,” said Alix Contosta, a research professor at UNH who studies ecological impacts of climate change. “That really does affect our ecosystems and has implications for our day-to-day lives.”
Cold weather matters — it kills certain pests and allows snow to stick around, which insulates the roots of trees, protecting them from damage. And snow also provides habitat for wildlife.
It’s an economic driver, responsible for a half-billion-dollar-a-year industry, according to an economic impact study by Ski NH. Jessyca Keeler, the executive director of that organization, said resorts opened a week later than usual this year because temperatures around Thanksgiving were too warm. Resorts are making snow because of a lack of natural snowfall, but that technology is limited by warmer weather. “My concern is that if the warming trajectory continues on that upward climb, we’re going to see shorter and shorter windows of opportunity to make snow,” Keeler said.
“If we’re projected to keep climbing, climbing, climbing, that doesn’t bode well for our industry,” she said.
Maple syrup producers are also already feeling the impact of warmer winters and less snow.
Steven Roberge, a forester with the UNH Cooperative Extension who grows sugar maples at his home in Peterborough, said strange weather patterns can disrupt the harvest. Maple sap harvesting is triggered by the seasons changing from winter to spring, when there are cold nights and warmer days. “That freeze-thaw cycle allows for sap to flow,” Roberge said. Already, the season for sugaring has changed. It used to start in late February but now begins a few weeks earlier, according to Roberge.
Sap flow is driven by weather, but weather isn’t the same as climate.
UNH climate scientist Cameron Wake said the difference between the two is that weather is what’s happening outside right now, while climate is a measure of long-term averages. The two are connected, he said: The weather is a result of the climate system. And as we change the climate system, the weather is also changing.
Snow also plays an important role in regulating temperatures. As there are fewer days where snow covers the ground, things can heat up more quickly, accelerating the warming process. Snow reflects solar radiation back into the atmosphere, and without it heat is absorbed into the ground. Wake describes this as a vicious cycle, or a positive feedback loop. This phenomenon — called the snow Albedo feedback loop — is one reason New England is warming so fast.
Another possible driver is our proximity to the Gulf of Maine, which is warming at one of the fastest rates in the entire world. The Gulf of Maine is shallow, and it’s a battleground between two currents, the Labrador Current, which brings cold water from the north, and Gulf Stream waters from the south. Osterberg described it as a tug of war between the warm and cold water, with the warm waters from the Gulf Stream currently winning out.
The loss of cold conditions across New England is something we need to think about deeply, Contosta said. Many people see the winter as a nuisance: It snows and you have to clear the driveway; it’s cold and uncomfortable to get outside. But extreme cold temperatures, and snow, are vital to the region. “I think of winter as the underdog season, an unsung hero of our four seasons,” she said.
Long-term forecasts predict above-average temperatures across the Northeast this winter, from January to April, in line with climate model predictions. And moving forward, we can expect more rain during the winter, as the same amount of precipitation falls but more as rain instead of snow.
As a scientist, Contosta has studied the vernal window — the period of time from when snow has melted until the forest canopy is leafed out. This period is changing a lot as a result of climate change. Winter is ending earlier, and spring is starting earlier. But those two things aren’t happening at the same pace (snow melt is happening faster than leaf out), and the vernal window is getting longer.
She said those changes are confusing the way we relate to the natural world.
“There’s a seasonal rhythm to our lives that gets disrupted by a changing climate in ways that can be personally hard to deal with on a day-to-day level,” she said.