Climate change made record-breaking Eastern Canada heat wave 'much more likely'

A new first-of-its-kind analysis says the record-breaking heat wave that enveloped Eastern Canada last month was made "much more likely" because of human-caused climate change.

Environment and Climate Change Canada says the results of its rapid analysis into the mid-June heat wave over parts of Ontario, Quebec and Atlantic Canada show it was made two to ten times more likely due to climate change.

It marks the public debut of Canada's new rapid extreme weather event attribution pilot program, which officials say can determine whether and to what extent climate change made a specific heat event more likely.

Environment and Climate Change Canada is thought to be one of the first government offices in the world to publicly roll out a rapid attribution tool and automatically apply it across the country, with results prepared within several days.

Federal officials say they eventually plan to apply the program to other weather extremes, such as precipitation, and there is work ongoing to also extend it to wildfire activity.

Scientists say attribution studies can inject climate science into public discussions of specific extreme weather events when it's most relevant, while underlining the effects of planet-warming emissions.

Hundreds of attribution studies have been published over the past two decades, largely keeping with the same general premise.

Researchers run climate models under two scenarios, one based on a simulation of a pre-industrial climate and another based on a simulation of the climate we have now. They then compare the results to an observed heat wave to figure out how much it was influenced by human-caused global warming.

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 those with Environment Canada, on dozens of studies over the past decade that have helped standardize research practices.

Shortly after a heat wave relented over Mexico last month, the group released a report suggesting it was made 35 times more likely and about 1.4 degrees hotter due to climate change.

The analysis comes on the heels of new results showing June marked the 13^th straight month of record-breaking global temperatures. It also marked the 12^th straight month where temperatures were 1.5 C warmer than pre-industrial times, according to the results released this month by the European climate agency Copernicus.

The 1.5 C mark is also the warming limit countries agreed to as part of the 2015 Paris climate agreement, though scientists note it won't be considered crossed until there’s longer-term duration above that threshold, as much as 20 or 30 years.

This report by The Canadian Press was first published July 9, 2024.