Environment Canada says it can now rapidly link high-heat weather events to climate change

Environment and Climate Change Canada says it's now able to publicly identify links between episodes of extreme heat and climate change within days of a weather event.

The federal department says that its scientists now have the ability to estimate the degree to which human-induced climate change played a role in a heat wave or extreme heat event within a week of it happening.

Friederike Otto, an internationally renowned climate researcher and one of the global leaders in weather attribution science, said Canada's weather service will be the first in the world to issue rapid analyses of heat events.

"The would be the first (meteorological office) who will do this operationally," he said.

"It's about time but it's great that they are doing that."

The science of weather attribution has existed for years. It combines meteorology, weather observation and climate science.

The science does not say whether climate change caused a specific weather event. Rather, it estimates the statistical likelihood of climate change causing a specific weather event and the degree to which it made the event worse. It also can indicate the opposite — that climate change did not play a significant role in a specific weather event.

"It will not answer the question, 'Was this climate change, yes or no,'" Otto told CBC News.

For example, a paper cited by Environment and Climate Change Canada (ECCC) concluded that the heat wave that hit British Columbia, Washington and Oregon in June 2021 would have been 150 times less likely in the absence of human-induced climate change.

The same paper said that in November 2021, human-caused global warming made the extreme rainfall that caused flooding in B.C. about 45 per cent more likely.

ECCC is launching a pilot project which will see its scientists study heat waves in Canada through computer modelling.

The department says it will run computer models on such heat events when they occur to compare two scenarios — one with a heat wave caused by climate change, the other with a heat wave in the absence of climate change.

The department says it is working to expand this system to include extreme cold weather events and extreme precipitation.

Climate attribution science emerged in part from journalists' questions about the links between climate change and specific weather events — questions that climate scientists like Simon Donner of the University of British Columbia have been unable to answer conclusively.

Donner compares it to a cancer diagnosis.

"We know that cigarette smoking causes lung cancer, but your doctor is not going to tell you which cigarette will be the one that gives you cancer," Donner said.

"And so we know climate change causes more heat waves, more heavy rainfall and more storm surges. But we can't look at the heat wave and say exactly, 'This one is caused by climate change.'"

Climate scientists have changed their approach to such questions, he said, by looking for models that define the likelihood of climate change playing a role in a specific weather event.

"So everything's being affected by climate change. So the question really is, how much more likely or how unusual is this event?" he said.

A man sprays water over his head at a public water station in Vancouver, British Columbia on Monday, June 28, 2021.
A man sprays water over his head at a public water station in Vancouver on Monday, June 28, 2021. (Ben Nelms/CBC)

Nathan Gillett, a research scientist with Environment and Climate Change Canada, said businesses and governments could use weather attribution analysis reports in the wake of extreme weather events that destroy infrastructure — like the 2021 atmospheric river event that washed out bridges in B.C.

"If you're rebuilding those bridges soon after an event, it's helpful to know whether the event was made more likely because of human-induced climate change and whether it's expected to become more likely in the future," Gillett said.

"If we're able to provide those results days after an event rather than months or years, they're likely to be of more interest to people to help understand the impacts of climate change."

Gillett contributed to the weather attribution analysis report published in December 2022 that concluded B.C.'s June 2021 heat dome "would be at least 150 times less common without human-induced climate change."

During that extreme heat event on June 30, 2021, the town of Lytton set a Canadian all-time temperature record of 49.6 degrees. A wildfire swept through the community a day later, destroying most structures. A couple in their 60s died sheltering in a trench from the flames.

Meghan Fandrich lost her business, a cafe she ran in Lytton. She said she welcomes the promise of rapid post-event analysis.

"I hope that it helps Canadians to overcome the distance they feel between themselves and the consequences of climate change," Fandrich told CBC.

"I hope it helps them to overcome the apathy that they feel, in that our actions now don't make a difference."