Experts: State on track to experience less snow
Researchers say climate change has ‘strong effect’ on New England
Connecticut has had three snowfalls so far in January. Two were in the past week on Tuesday and Friday. A larger storm came through on Jan. 7, dumping over a foot of snow on some of the more northern towns in the state.
But if you were thinking that this winter has been fairly mild so far, it isn’t your imagination. Connecticut has had a fairly mild winter following an abnormally hot, smoky summer and warm autumn. New research from Dartmouth College in New Hampshire says that snowpack has declined since 1981, and that climate change is to blame.
“New England is one of the places where we’re able to identify a quite strong effect,” said study author Alexander Gottlieb, a graduate student at Dartmouth College. “Something like 30 to 40 percent smaller spring snowpacks now versus back around 1980 just due to humancaused climate change.”
Snow is a perennial topic in environmental circles. People in snowy areas instinctively compare snowfalls year to year, decade to decade, as barometers of climate. Denialists cite heavy snowstorms or incidents of snowfall as “evidence” that climate change is a hoax.
“Basically, my whole life everyone you talk to has this anecdotal sense of winter, that it’s getting less cold and less snow,” said Gottlieb. “A lot of people have an emotional attachment to snow and it’s the thing we sort of intuitively use to benchmark the advance of warming.”
But snowpack can be hard to measure over large regions. Snow doesn’t fall or melt evenly. Gottlieb says that our memories of snow tend to be a little unreliable.
“We have short memories, we worry about long-term declines but then you get a big snowstorm or a big snowy winter and in your mind you return to baseline,” said Gottlieb. “It obliviates a lot of the concerns in the short term then you start racking up more low-snow years and get concerned all over again.”
To overcome this, and the “noise” in snowfall data, Gottlieb and his research mentor Justin Mankin, a geography professor at Dartmouth, combined 550 35-year weather data sets from weather agencies across the northern hemisphere that had complete snowfall records. They combined this data with precipitation and runoff data and then compared this to 12 climate models.
“By combining all of these snow data sets and climate model simulates with and without human emissions we can generate a lot of estimates about what long-term snowpack trends might have been doing absent our emissions,” said Gottlieb. “It is almost impossible that we would observe what we do in the real world due to natural variability alone.
They found that snow was sensitive increased global temperatures but that the relationship was non-linear. It wasn’t a simple “more heat less snow” situation. Some places were more sensitive to increased temperature than others, with respect to snowfall.
Watersheds that historically experienced average winter temperatures of around or above 18 degrees fahrenheit were the most sensitive. Each degree warming (on the Celsius scale) sharply decreases the average amount of snowfall by about 5 to 10 percent
“In places like this, even modest amounts of warming … can wipe out an incredibly large chunk of your snowpack,” said Gottlieb.
The Connecticut, Hudson, Merrimack, Delaware, and Susquehanna river basins experienced the sharpest declines in annual snowpack since 1981.
“We’re well above the threshold where our snowpack is going to be really sensitive to temperature,” said Gottleib. “The warming we’ve seen so far that’s caused us to lose a lot of snow.”
This doesn’t mean we wont ever see snow again, just that the pattern of snowfall, and the average snowfall are changing. Guiling Wang, a climate scientist at UConn who worked on the Connecticut Physical Climate Assessment said that the area would experience more “unstable” winters with more extreme storms.
“Think of the air as a sponge,” Wang explained that as the atmosphere warms it can hold more water vapor. “When you have more moisture in the air that essentially makes rain more intense.”
In warmer months, all this extra water vapor and thermal energy can mean more extreme rain. In the winter, if it’s cold enough, that can mean more snow falling at once.
“In polar regions it snows less times because there isn’t much moisture to precipitate out, you
need moisture to make snow,” said Wang.
“In a warmer world, in the winter, if there is more moisture in the air when a cold front comes that moisture will precipitate out.”
Wang said that a warmer atmosphere also meant a more unstable circumpolar current. Historically the circumpolar current was kept tight by a large temperature gradient between the equator and the poles. As that gradient breaks down the current gets “looser” and bulgier. Arctic air can bubble out of the north more easily, causing
cold snaps.
In that situation, both extreme cold and extreme snow are possible, Wang explained. In a warming world, these cold snaps are followed by unseasonal thaws and rains.
“You might have one-off individual storms or winters that are really snowy,” agreed Gottlieb. “Due to natural variability in the climate system, sometimes the ingredients line up for a big storm, but as things go ahead that’s just going to be increasingly less likely.”
Overall this means less snow, less predictable weather and
less cold days punctuated by extreme winter weather. Gottlieb said this was a recipe for ecological, infrastructural and agricultural problems.
“In the same way that we’ve build our systems and our infrastructure on the expectation of what winters should look like, all the forests, plants and animals that have been evolving in this place have encoded that expectation,” said Gottlieb, referring to persistent snowpack. “It’s a very active area of research trying to understand what the ecosystem consequences of snow loss are.”