Paradox between warming climate and intense snowstorms, say scientists

Paradox between warming climate and intense snowstorms, say scientists

FREDERICTON – There is a complex, counterintuitive relationship between rising global temperatures and the likelihood of increasingly intense snowstorms across Canada.

FREDERICTON – There is a complex, counterintuitive relationship between rising global temperatures and the likelihood of increasingly intense snowstorms across Canada.

Winters are on average milder and warmer than they used to be, but extreme weather events like heavy snowstorms have also increased across the country, said John Clague, a professor of geosciences at Simon Fraser University in Burnaby, BC

People might find it illogical that parts of the country experience more snowstorms as the climate warms, he said. “What climate modellers have found is that climate change brings with it more frequent extremes.”

“That means you can have extremely high temperatures in the summer, life-threatening high temperatures like those experienced in India and Pakistan in recent years. And you can have these extremely cold conditions even in winter.”

One of the reasons for the extremes is the jet stream – defined by Environment Canada as “a narrow band of strong winds about 10 kilometers above the Earth that marks the dividing line between warm and cold air masses”.

Clague said the jet stream, which moves west to east and carries weather systems with it, moves more slowly than usual and appears to park over an area for a period of time. The mass of cold or hot air it carries lingers in the atmosphere, where it collides with moisture-laden currents and causes heavy snow or rain, he said.

“This interface between this moist, temperate air at lower latitudes and the cold, drier air — the Arctic air — creates snowfall.”

Kent Moore, a professor of atmospheric physics at the University of Toronto, said it’s paradoxical that climate change is producing increasingly intense snowstorms. There is some evidence that warming Earth is changing the dynamics of how the jet stream works, he said.

The jet stream can have “bigger ripples” as the climate warms, meaning it just doesn’t go west to east, but sometimes travels north or south like a wave, he said. It also pulls arctic air with it as it moves south, he added.

“There is evidence that the jet stream is becoming more rippled as the climate warms,” ​​Moore said.

The interplay between declining sea ice and a rapidly warming Arctic is reducing the temperature gradient from the southern tip of the country to the north, he said. And a rippling — or weakened — jet stream brings arctic air south, creating intense snowstorms, he added.

The oceans on both coasts also play a role, as warming climates lead to more evaporation of water, Moore said. “That means there’s more water vapor in the atmosphere, which means there’s more snow because of it.”

Blair Feltmate, director of the Intact Center on Climate Adaptation at the University of Waterloo, said warmer air holds more moisture and has more heat energy than colder air. “This often leads to heavy precipitation in the form of more rain in summer and snowstorms in winter,” he said.

Average global temperatures have risen by about 1.1C to 1.2C over the past century, he said, adding that Canada has warmed even more. The southern half of Canada has warmed about twice as much as the global average, he said. The northern half, meanwhile, has been heating up about three times faster, he added.

“This leads to atypical or atypical weather in different areas of the country. It’s not just that we may have more snowfall as we are now seeing, we may also have extreme cold snaps.”

Feltmate said the intensity of the top 1 percent of precipitation events that occur in a single year has increased about 37 percent toward the western end of the Great Lakes and 72 percent toward the east over the past six decades.

Moore, who has studied snowfall in the Toronto area, said that in a typical winter, the amount of accumulation decreases as the amount of rain increases. “That’s not to say there can’t be a really, really bad storm that kicks up tons of snow in a few days. That can still happen, even if the long-term trend is towards less snow.”

Feltmate said the symphony of winter storms from Vancouver to Toronto and the Maritimes can be attributed to climate change. He used a baseball analogy to illustrate the connection between climate change and recent severe weather events – the heat dome, atmospheric fluxes, post-tropical storm Fiona and “mammoth” snowstorms.

“It’s a bit like saying you have a baseball player who’s been on steroids. And suddenly this baseball player starts hitting five times as many home runs,” Feltmate said.

“You can’t say a single home run was due to the steroids. But if he or she hits five times as many home runs, then it’s pretty fair to say that there is cause and effect between taking the steroids and succeeding. With climate change, we have extreme weather on steroids—and steroids are here to stay .”

This report from The Canadian Press was first published on December 24, 2022.

Hina Alam, The Canadian Press

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