Climate change made June heat wave up to 10 times more likely, scientists say – National

The above-normal temperatures in Ontario, Quebec and Atlantic Canada were made two to 10 times more likely as a result of human-caused climate change, Environment and Climate Change Canada scientists said on Tuesday.

The agency announced the results of its analysis from its new rapid extreme weather event attribution system, a tool meant to determine the degree to which climate change affects extreme climate events.

Data released on Tuesday analyzed extreme temperatures in mid-June from four sub-regions: Eastern Ontario, Southern Quebec, Northern Quebec and Atlantic Canada. Scientists are expected to release similar analysis for the heat events in Western Canada later next week.

“In all regions, the event was made much more likely as a result of human influence on the climate,” Greg Flato, senior research scientist at Environment and Climate Change Canada, said.

“By ‘much more likely,’ we mean that the event was at least two to 10 times more likely than it would have been in the absence of human-caused climate change,” he said.

The agency said that from June 17 to 19, a heat wave reached a peak temperature of 29 C (average) over the Eastern Ontario sub-region, which is 7.4 degrees above normal.

Of the four regions, Southern Quebec saw the highest above-normal increase between June 18 and June 20, with a peak temperature of 29.5 C averaged over the region, which is 10.7 degrees above normal.

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In the same period, Northern Quebec saw a peak temperature of 21.5 C averaged over the region, which is 7.2 degrees above normal. In Atlantic Canada, within the same period, a heat wave reached a peak temperature of 26.1 C, which is 10.6 degrees above normal.

The rapid extreme weather event attribution system is able to simulate the weather system of the late 1800s, before the worst impacts of the Industrial Revolution, and compare it with today. Scientists then analyze to what extent the increase in greenhouse gasses in our atmosphere makes such extreme weather events likely.

While the system is only geared to measure the impact of climate change on heat waves, scientists hope to expand it to analyze cold weather events and extreme precipitation as well.

The three categories for heat waves are more likely (up to twice as likely because of climate change), much more likely (two to 10 times more likely because of climate change) and far more likely (more than 10 times more likely because of climate change).

“What the rapid event attribution system allows us to demonstrate is the effect of that human-caused climate change increasing the likelihood or the intensity of heat waves like this. We also do projections of future changes in not only average conditions but extremes,” Flato said.

A sizzling heat wave has Canada and the United States in its grip as a global streak of hottest-ever months continues to shatter records.

Heat warnings were in place on Monday in parts of eight provinces — British Columbia, Alberta, Saskatchewan, Ontario, New Brunswick, Newfoundland and Labrador, Prince Edward Island and Nova Scotia — as well as the Northwest Territories.

Environment Canada is forecasting that B.C.’s Southern Interior could see temperatures climb into the low 40s C this week.

Temperatures in Alberta and Saskatchewan are expected to reach at least 30 C, with some parts of Alberta forecast to hit about 35 C by Wednesday.

In Atlantic Canada, daytime highs are forecast to top 30 C across much of the region.

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