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Experts quiet climate-change skeptics

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Climate-change skeptics — and everyone else in Canada — had better bundle up. Research shows extended cold snaps like we’ve seen this winter could be a direct result of climate change.

In a Rutgers University paper published last year, researchers Jennifer Francis and Stephen Vavrus wrote that the melting of Arctic ice was weakening the jet stream, the band of fast-moving wind that separates colder northern air from warmer air further south. As it weakens, it dips southward for longer periods than in the past, bringing icy-cold air with it for increasingly long stays.

The weaker winds “may lead to an increased probability of extreme weather events that result from prolonged conditions, such as drought, flooding, cold spells and heat waves,” says the article, published in Geophysical Research Letters.

That means that while the climate (or average global temperature) of the Earth heats up, the weather in every region won’t necessarily follow suit. Places prone to warm weather will see extended droughts, while much of Canada may experience more extended cold snaps.

In other words, a warmer Arctic may be affecting the length of time the polar vortex dips down south, but not necessarily the temperatures themselves. Further, as the Arctic continues to heat up, so may the temperature of the “cold snaps,” reflecting the warming northern air.

The authors have faced criticism from some peers, particularly scientists who say linking climate change to the polar vortex distracts from the greater discussion about global warming. As part of a response to one critical letter about her theory, Francis gave this comment to the New York Times:

“Carefully designed modeling experiments and additional years of real-world data are needed to confirm it or not. To me, the ample discussion this idea has generated is not a ‘distraction,’ but rather a trigger of a great deal of new research and healthy scientific discussion.”

Climate versus weather

Francis’ theory aside, the recent deep freezes have been accompanied by plenty of chatter from climate change skeptics. News-story commenters and TV pundits have often mused about how it’s possible a warming Earth could produce record lows.

The sort of confusion we’ve seen in the public around this issue belies a misunderstanding of the difference between climate and weather, said Dr. Altaf Arain, director of the McMaster Centre for Climate Change in Hamilton, Ont. He thinks people tend to look at their local weather for evidence of climate change, when really it’s the global average that shows the trend.

“When people see one month of extreme cold, they say ‘What happened to global warming?’” said Arain, a professor in McMaster University’s School of Geography and Earth Sciences. “But if you look globally, it’s -23 C in our region, but in Australia, in Europe the temperatures are much warmer than usual.”

He supports the Rutgers research, and adds that reduced Arctic sea ice and extended weather periods have both been studied extensively. The theory that a weakened jet stream explains longer weather patterns is the “most plausible explanation that we have,” he told on Wednesday.

The Earth is understood to be warming at about .1 to .2 degrees Celsius per decade, a pattern that holds true even when certain climates face cold snaps, he said. Arain pointed at droughts in California and floods in England, happening at the same time as our extreme weather.

“If we look at Ontario and Eastern Canada, we will see a cooler year. But on the global scale, these lower temperatures might not have much impact. We were -20 C while other places are 10 or 20 degrees higher than usual. It will be very interesting to see our global (average) temperature for 2014.”

The heavy snowfall many Canadians have seen this year may also be linked to global warming, Arain added. As temperatures rise, more water evaporates into the atmosphere, speeding up what is known as the “hydrological cycle.”

“When it’s accelerated, you have more evaporation; more rainfall or snow,” Arain explained. “Our annual numbers may not change that much, but we will have a downpour and then a dry period. This is part of the discussion about prolonged weather patterns.”

Get ready

While it may be decades before we see environmental catastrophe due to changing temperatures, governments and individuals would be prudent to start planning now, Arain warned. Increased rains, flooding, snowfall and temperature shifts come with a cost, particularly as buildings, streets and cities face weather extremes for which they weren’t built.

“On the ecosystem side, the costs come slowly. But burdens on insurance, damage to infrastructure, increased energy bills; these are happening now.

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