Winters in southern Manitoba are getting warmer, shorter and less snowy.
New research from a consortium of American and Canadian scientists, supported by the New Hampshire-based nonprofit Hubbard Brook Research Foundation, measured the effects of climate change already being felt in the region, through the Great Lakes and down the eastern seaboard, as far south as New York.
In the study, titled Confronting Our Changing Winters, scientists found in the last 100 years, in the western region of their research zone (which includes southern Manitoba and northwestern Ontario), the number of cold days below -30 C have already dropped by an average of five a year.
Meanwhile, the number of days with temperatures below -18 C have declined by an average of 14 per year.
University of Winnipeg associate Prof. Nora Casson explained these cold-weather temperature thresholds are important for forests, because it helps keep pests in check.
"For instance, at -17, it’s cold enough to kill about half of southern pine beetles, and if temperatures drop to -22, very few can survive," Casson said. "If you lose really cold days, there’s a bigger risk of invasive forest pests that are bad for forest ecosystems."
The changes in winter are also affecting recreational activities across Canada and the United States.
One of the measures the report looked at was "snowmaking days," where the minimum daily temperature reaches at least -5 C. Prior to Christmas, the number of days that qualify as snowmaking days has dropped by 15 in this region.
This has implications for everything from ski resorts to snowmobile trails being unable to open at the end of a calendar year, Casson said. In Winnipeg, the progressively later opening of The Forks skating trails is a prime example of the shortening winter season.
Additionally, through the entire year, the number of days where there’s snow cover on the ground has fallen by 17 days, the study says.
Reduction of the snowpack can be hard on forests, as frozen soils can damage root systems, and rodents and other small mammals often rely on the snowpack for survival in the winter. Declining numbers of small mammals, which has already been documented, can then have spillover effects felt through entire food chains and food webs.
The review of weather records over the past 100 years showed winter is, on average, 14 days shorter already across the upper Midwest U.S. and Canadian southern Prairies. The report concludes changes to snow and cold weather in areas that are adapted for the conditions will have sizable impacts on social, economic, and environmental systems.
Casson said the report aimed to make the changes in the winter season more relatable for the general public — something less abstract than how much the earth has warmed on average. It's also proof of what has already happened as a result of climate change, instead of some forecast for something decades down the road.
"The winters our children and grandchildren experience depend on the choices we as a society make today," Casson said. "It’s in our hands to change the course we’re on and protect some of the things we really value about winter."
Sarah Lawrynuik reports on climate change for the Winnipeg Free Press. Funding for the Free Press climate change reporter comes from the Government of Canada through the Local Journalism Initiative.