Climate change has made it more likely for Canada to record its warmest December in more than 50 years, a temperature anomaly that stood out from the rest of the planet, a new study finds.
“This really stands out on a global level,” argues Andrew Pershing of Climate Central, a nonprofit group of scientists and science journalists based in Princeton, New Jersey.
“When you start to broaden the horizon, you realize how unusual the situation was in Canada,” he adds.
The month of December actually broke heat records across the country, particularly in the Prairies.
On December 6, Alberta alone set seven new records. That day, Bow Island in the south of the province recorded a temperature of 18.6°C, 5.8 degrees warmer than the previous record in 1962.
All provinces and territories experienced above normal temperatures, but the Prairies recorded the highest temperatures. Manitoba recorded 8.6 degrees warmer than normal, Saskatchewan 8 degrees and Alberta 7.1 degrees.
The impact of climate change
This year, the El Niño phenomenon, a weather pattern that usually brings warm weather, has been very present. However, this was not the case for the month of December, says Mr. Pershing.
“What we see is the constant push of climate change, day after day,” he says.
Pershing and his colleagues used the Climate Shift Index (CSI) to determine the impact of climate change. This index uses a well-established, peer-reviewed methodology to determine the influence of climate change on each day’s weather conditions.
The index is a common tool for climate scientists, says Nathan Gillett, who studies weather attribution at Environment Canada.
“The Climate Shift Index has been around for some time,” he says. It is generally well accepted. »
Weather attribution studies are increasingly popular and have examined the role of climate change in a wide range of events around the world, including the recent disastrous wildfire season in Canada.
For the month of December, Pershing added up the number of days in each province for which the CSI was greater than two, meaning that climate change made that day’s temperature at least twice as likely.
Ontario and British Columbia have had 11 such days. Manitoba had 10. Quebec had nine. Saskatchewan and Alberta had an average of five.
It’s not just El Niño, Pershing said. Previous strong El Niño years have been nothing like what happened in 2023.
“We wouldn’t get the records we saw because of El Niño. The records are due to climate change, with El Niño adding a little extra flavor,” he explains.
Mr. Gillett, who was not involved in the Climate Central study, emphasizes that the findings were what he expected.
“The results are credible and the conclusions are logical,” he says. They are confirmed by other data I have seen recently. »
How to explain the cold snap?
In January, temperatures dropped across the country.
According to Pershing, the relationship between climate change and cold spells is not yet clearly established. Some think Arctic warming weakens the jet stream and contributes to events like the current wave, but that’s not conclusive, Pershing says.
Natural variability still exists, Mr. Gillett said. “There is still variability and these kinds of events can still happen,” he said. But they are less likely than they would have been in the absence of human-induced climate change. »
You have to get used to it, says Mr. Pershing, if you can.
“I can go out on these warmer winter days and be very happy and very scared at the same time,” he says.