Extreme cold and climate change: What's the deal?
Why are we breaking Canadian records amid record global heat?
In the past week, extreme cold has hit many parts of Canada, including –40 C temperatures in Manitoba, Saskatchewan, and Alberta, where the record-breaking cold led to electricity shortages.
B.C. experienced both record cold and unusually heavy snow, and much of the snow fell in parts of the province that aren't usually snowy, closing schools and downing trees and power lines.
And yet, we've just heard that globally, the world has just set a new heat record for the hottest year, and cyclical warmth in the Pacific Ocean, called El Nino, is supposed to make it even warmer.
So what's going on?
Well, even in a warmer world extreme cold can happen. But also, scientists are examining how the two phenomena may be linked — and that by altering global systems, extreme cold might become more likely.
Here's a closer look.
Is this weather really unusual?
Yes, confirmed Jesse Wagar, a warming preparedness meteorologist with Environment and Climate Change Canada in an interview last week. "In the wintertime we do get these really dynamic weather patterns, but I think the intensity of the systems that are moving through right now in this weather pattern is pretty unusual."
And, of course, the records for coldest temperatures recorded for a given day of the year in many places speak for themselves.
Is this evidence that global warming may not be really happening?
No. Global warming represents climate change — long-term trends — on a global scale, and a variety of measurements have shown a clear overall warming trend.
What's been happening in parts of Canada is weird weather — something short-term and regional.
Steve Easterbrook, the director of the School of the Environment at U of T reminds people that, "Climate change does not remove winter so we're always going to have winters. What climate change does is it just shifts all those temperatures up a little on average."
"No single weather event can prove or disprove global warming," explained Matthew Barlow, a professor in the Environmental, Earth and Atmospheric Science Department at the University of Massachusetts Lowell in a recent article in The Conversation.
Megan Kirchmeier-Young is a research scientist with Environment and Climate Change Canada who uses climate models to figure out whether certain extreme weather events can be linked to climate change.
She noted that even as climate change warms the Earth, there are still seasons and natural variability in day-to-day temperatures. "We still have very cold days."
But shouldn't climate change mean fewer cold snaps?
Yes, and overall, that's what has happened, Kirchmeier-Young says.
"In general, cold extremes are becoming less frequent," she said.
Not only that, but the temperatures during cold snaps are becoming warmer.
In fact, the record temperatures we saw in recent weeks would "most likely" have been even colder without climate change.
"As we continue warming, it is less likely that we will be breaking cold records," she added, "but we may."
Easterbrook says that while the cold snaps aren't as extreme, we may being seeing them more frequently. This is due to the jet stream being less stable and "that means some of those Arctic weather patterns, the really cold snaps, like we've seen this week, that's kind of Arctic wind blowing down further South than they normally come."
What we've been breaking much more frequently is heat records. In fact, some parts of Canada, are setting new heat records even as other parts of Canada set cold records.
On Tuesday, it hit 3.3 C in Iqaluit, breaking a record of 0.8 C set in 1977. Today, Rankin Inlet, even further north, was forecast to hit the record high of –5 C.
In fact, the hot and cold extremes are related, Environment Canada meteorologist Justin Shelley told CBC News.
No doubt you've heard about the stratospheric polar vortex, cold, icy weather that usually stays high above the Arctic in winter, but sometimes stretches south, bringing Arctic temperatures with it. Shelley said that's what's causing the record cold in the West.
"As the flip side of that really cold air sinking over Western Canada," he added, "it's pulling over really mild air from the south over some parts of Eastern Canada but primarily over northern Quebec and Nunavut."
Is climate change making some cold snaps more intense?
Kirchmeier-Young says the polar vortex "isn't a new thing; we've always had this cold air from the Arctic coming down and giving us cold extremes."
But it's an "open question," wrote Barlow, whether climate change is making that happen more often.
"Some research suggests it does," including his own. He co-authored a 2021 study in Science linking warming in the Arctic with changes to the polar vortex and extreme cold events such as the deadly cold snap in Texas in 2021.
Barlow and his colleagues used modelling to show that changes to snow and sea ice cover in the Arctic due to climate change can be linked with stretching and waviness of the polar vortex — bringing cold temperatures south.
Other researchers, such as Judah Cohen of Atmospheric Environmental Research, a commercial firm outside of Boston, have found that polar vortex "outbreaks" have become more frequent in recent decades.
But others, such as Amy Butler, a research scientist with the U.S. National Oceanic and Atmospheric Administration, who studies the stratosphere, have noted that records of the polar vortex don't go back far enough to understand its natural variability, and there hasn't been a clear trend.
Meanwhile, some researchers have modelled that warming will do just the opposite of what Barlow found and make the polar vortex weaker.
Kirchmeier-Young says, "There's still a lot of uncertainty and unanswered questions in terms of the relationship there."
Corrections
- A previous version of this story referred to the Gulf Stream contributing to more frequent cold snaps. In fact, it is the jet stream.Jan 25, 2024 6:02 PM ET
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With files from Anna Spencer
