(Toronto) The heat wave that hit Eastern Canada last week caused sweltering conditions, put pressure on the power grid and led to several temperature records.

Even though the unusually high temperatures have now subsided, fundamental questions remain: How much more likely was this heat wave due to climate change? And how much worse has the situation gotten because of it?

Within a few days, researchers from Environment and Climate Change Canada should have answers.

The data will be revealed as part of a new Canadian pilot project for rapid attribution of extreme weather events. Environment Canada will be able to say, about a week after the end of a heat wave, whether and to what extent climate change has made it more likely or more intense.

Environment and Climate Change Canada would be one of the first government offices in the world to publicly deploy such a tool and automatically apply it to heat waves across large regions of the country.

“I think it’s an important step,” said Nathan Gillett, a research scientist at Environment and Climate Change Canada, who has helped lead the pilot since it was approved in 2022 as part of the country’s national adaptation strategy. federal government.

Climatologists have long explained how emissions linked to global warming make extreme weather events – from heat waves to heavy precipitation – more likely and more severe across Canada. Temperatures that would have been virtually impossible without the burning of fossil fuels are becoming the new extremes, scientists warn.

Faster data

However, studies of these heat waves or floods can take months to appear in a peer-reviewed scientific journal.

By then, policymakers may have debated how to rebuild or where to relocate after a devastating flood, for example, without a clear indication of the role of climate change. Public attention and the news cycle have moved elsewhere.

Rapid studies, popularized over the past decade by pioneering international research groups, seek to inject climate science into the debate where it is most relevant.

Take, for example, the bridges destroyed in the 2021 floods in British Columbia, Gillett suggested.

“If you’re rebuilding these bridges, it’s useful to know whether the event has been made more likely by human-induced climate change, and also how that likelihood might change in the future,” said Gillett, co-author of a study that found the event in British Columbia was 45 per cent more likely because of human-induced warming.

Attribution studies generally follow the same basic principle. Researchers run climate models under two different scenarios. One scenario is modeled on a pre-industrial climate before humans began burning fossil fuels, and a second is based on a simulation representing the climate as it is today.

Scientists then compare these results to an extreme weather event, such as the heat wave in Eastern Canada, to determine how it may have been influenced by human-caused climate change.

Gillett said the pilot project will eventually be applied to other extreme weather conditions, such as precipitation and cold temperatures, and work is underway to expand it to wildfires.

A “big step forward”

While many national weather agencies carry out attribution studies, Canada’s engagement in a rapid study program of this scale is a striking example, said Sarah Kew, a climate researcher at the Royal Meteorological Institute. Netherlands and World Weather Attribution.

“This is a big step forward in attribution,” she argued.

World Weather Attribution, which is made up of a team of international researchers, has been at the forefront of rapid attribution science, collaborating with local scientists, including Environment Canada’s Gillett, on dozens of studies over the past decade that have helped standardize research practices.

Days after a heat wave abated in Mexico earlier this month, World Weather Attribution released a report suggesting it was 35 times more likely and about 1.4 degrees warmer due to climate change.

Attribution studies also look at what might be natural climate variation, rather than just human-induced climate change. A World Weather Attribution study of the southern African drought earlier this year found that El Niño, a natural climate cycle, was the main driver, not climate change.

“The climate is changing faster and faster. And we’re seeing more and more extremes every year. It’s really crazy how many extreme events are happening. So the questions are coming up faster and faster,” Kew said.

“It’s important that there are scientific answers at our fingertips. No biased answers, but answers that have been developed with a good and solid methodology. »

A call to action

More broadly, attribution science has also strengthened efforts to hold large emitters, such as oil companies, responsible for losses and costs related to specific extreme weather events.

Rapid attribution tools are best used as a call to action, said Rachel White, an assistant professor of atmospheric sciences at the University of British Columbia who uses climate models to study extreme weather events.

“All it does is show how serious the problem is; we still need to stop making the problem worse,” she stressed.

“We must reduce our greenhouse gas emissions very quickly, and in a way […] rapid, equitable and permanent. »