When heat waves strike, Environment Canada can make the link to climate change — fast

The heat wave that gripped Eastern Canada last week brought stifling conditions, put pressure on the electricity grid and broke several temperature records as residents sweltered.

While the unusually high temperatures have now relented, fundamental questions remain: just how much more likely was that heat wave because of climate change? And how much worse did it get because of it?

Within a few days, researchers at Environment and Climate Change Canada are expected to have the results.

The data would mark the public debut of Canada's new rapid extreme weather event attribution pilot program. Environment Canada will be able to say, within about a week of the end of a heat wave, whether and to what extent climate change made it more likely or intense.

Environment and Climate Change Canada is believed to be one of the first government offices in the world to publicly roll out such a tool and automatically apply it to heat waves across large parts of the country.

"I think it's an important milestone," said Nathan Gillett, a research scientist with Environment Canada and Climate Change Canada, who helped steer the pilot project since its approval in 2022 under the federal government's national adaptation strategy.

Climate scientists have long detailed how planet-warming emissions are making weather extremes – from heat waves to heavy rainfall – more likely and severe across Canada. Temperatures that would have been virtually impossible without burning fossil fuels are becoming the new extreme, scientists say, while extremes are becoming the new unusual.

Studies of those specific heat waves or floods can, however, take months to make it into a peer-reviewed scholarly journal.

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

Rapid studies, popularized over the past decade by trailblazing international research groups, look to inject climate science into the discussion when it's most relevant.

Take, for example, the bridges destroyed during the 2021 British Columbia floods, Gillett said.

"If you're rebuilding those bridges, it's useful to know whether the event was made more likely by human-induced climate change, and also to know how that likelihood might change in the future," said Gillett, who co-authored a study that indicated that B.C. event was made 45 per cent more likely due to human-caused warming.

Attribution studies typically follow the same general premise. Researchers run climate models under two different scenarios. One scenario is modeled on a pre-industrial climate before humans started burning fossil fuels, and a second is based on a simulation of our climate as it is now.

Scientists then compare those results to a defined extreme weather event, such as the Eastern Canada heat wave, to figure out how it may have been influenced by human-caused climate change.

Gillett said the pilot program will eventually be applied to other weather extremes, such as precipitation and cold temperatures, and there is work ongoing to extend it to wildfire activity.

While many national meteorological agencies do attribution studies, Canada's commitment to a rapid study program on this scale is a standout example, said Sarah Kew, a climate researcher with Royal Netherlands Meteorological Institute and World Weather Attribution.

"This is a great step forward for attribution," she said.

World Weather Attribution, which is made up of a team of international researchers, has been at the vanguard 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 relented over Mexico earlier this month, World Weather Attribution released a report suggesting it was made 35 times more likely and about 1.4 degrees hotter due to climate change.

Attribution studies also parse what might be natural climate variation, rather than just human-caused climate change. A World Weather Attribution study of drought across southern Africa earlier this year found El Niño, a natural climate cycle, was the key 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 the amount of extreme events that are happening. So, the questions are coming thick and fast," said Kew.

"It's important that there are scientific answers at hand. Not biased answers, but answers that have been developed with a good, solid methodology."

More broadly, attribution science has also bolstered efforts to hold big emitters, such as oil companies, responsible for the casualties and costs of specific climate-fuelled weather extremes.

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's doing is telling how bad the problem is; we still have to stop making the problem worse," she said.

"We need to be reducing our greenhouse gas emissions really quickly, and doing that in a way that ... is fast, fair and forever."

This report by The Canadian Press was first published June 28, 2024.