There’s a direct relationship between the temperature of the atmosphere and how much water it can hold, said Judah Cohen, a research affiliate at the Massachusetts Institute of Technology, who works as a director of seasonal forecasting at Verisk Atmospheric and Environmental Research.
“It’s like a sponge. If the atmosphere is very warm, it could hold a lot of moisture,” he said. “You put all the water in the sponge. And then as you slowly lower the temperatures, it’s like squeezing the sponge, and so all the water comes out of it,” he said.
Beginning Friday, the sponge got squeezed as a stalled low-pressure system off Nova Scotia’s coast dumped up to 150 centimeters of snow in parts of Cape Breton, prompting local states of emergency and a call from the province for federal help in digging out.
About 20 or 30 years ago, Cohen said, the consensus in the scientific community was that a warming world would result in less snow. But now it is believed climate change could lead to more intense snow and rain, he said.
John Clague, a professor of geosciences at Simon Fraser University in Burnaby, B.C., said ocean temperatures in the North Atlantic have increased in recent years, allowing temperate air masses along Canada’s East Coast to hold more water vapour. When this moisture-laden warm air comes into contact with arctic air, “crazy” amounts of snow fall, he said.
“In my view, it’s another example of extreme weather that may have the fingerprint of climate change on it,” he said of the recent Nova Scotia storm.
“No single extreme weather event can be attributed to climate warming, but we have been seeing far more of these extreme events around the world … It’s not inconsistent with climate change.”
Clague said the climate in North America is largely controlled by the jet stream. He described the jet stream as a continuous fast-moving band of air that sits high in the atmosphere. It separates polar air in the north from temperate air in the south.
“Over the past decade, the jet stream has become more snakey and unpredictable — wandering over a larger range of latitudes,” Clague added.
An atmospheric ridge caused by the jet stream twisted itself over the continent in an inverted horseshoe shape, making its impact felt on both the East and West Coasts, he said. The stalling of the jet stream caused the air ridge that hit the high pressure to be blocked from moving east, bringing days of rain in California and snow in Nova Scotia.
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