The record-breaking heatwave that ravaged western North America last June was among the most extreme on record anywhere in the world, according to new modeling and analysis by researchers from universities across the UK.
The study published Wednesday in the journal Science Advances found that only five other heat waves since the 1960s were more extreme, based on how far they exceeded the average summer heat over the previous 10 years.
The paper shows that extremes are warming as temperatures rise with climate change, said Vikki Thompson, senior research associate at the University’s School of Geographic Sciences and Cabot Institute for the Environment. of Bristol.
The study predicts that by 2080, heat waves like last summer’s could have a one-in-six chance of occurring each year in western North America as the effects of climate change increase. man-made worsen.
The projections are different depending on whether global climate change is contained, Thompson said in an interview Wednesday.
“We also include the emission reduction scenarios in our supplemental data so people can see, if policies change, where we might be instead,” she said.
“And that’s a much better picture, it would still be a 1,000-year event by the end of the century, if emissions were reduced.”
The study cites the example of Lytton, in the southern interior of British Columbia, where a national temperature record of 49.6 degrees Celsius was set the day before a rapid wildfire destroyed a large part of the community.
The British Columbia coroner has attributed nearly 600 heat deaths from mid-June to August, with 526 deaths in a single week between June 25 and July 1.
British researchers looked at daily maximum temperatures between 1950 and 2021 during two weeks of extreme heat, from June 24 to July 6, over an area spanning Vancouver, Lytton and south into the US Pacific Northwest.
This area was chosen because it was the warmest of most of western North America that felt the heat wave, Thompson said.
The study found that the highest average daily maximum temperature over these seven decades was 39.5°C on June 29, 2021. Over the previous 10 years, the average maximum temperature for the three hottest months each year was 23.4°C, she says.
Daily temperature extremes in this region last summer were “so much beyond that range, it was pretty exceptional,” Thompson said.
To understand the heat wave in a global context, researchers looked at 230 regions around the world, including British Columbia and Alberta. They compared the hottest temperatures recorded on a single day all year with the average of the three hottest months of the year over the previous decade, Thompson said.
The temperature recorded in Alberta on June 30, 2021 is listed as the sixth most extreme heat since the 1960s, with a maximum temperature of 36°C.
British Columbia’s daily high of nearly 50C was much warmer, but it wasn’t as far from normal because the province had a higher benchmark temperature than Alberta, Thompson said. The benchmark in Alberta was 22C, she added.
A combination of high atmospheric pressure and drought conditions across much of western North America helped fuel the heat wave, the study said.
To better understand future heat waves, the researchers used modeling of Earth systems that projected events of similar intensity in the same area.
“We can look ahead and see how much more likely that is 100 years from now, and the model we’re using suggests it’s going to happen one in six years, 100 years from now, so every decade we’re ‘I’ expect such an extreme heat wave,” Thompson said, referring to temperatures in western North America.
The researchers used a worst-case scenario for climate change, she noted.
“Thinking about the possible impacts, we want to know how bad it could be.”
People who have experienced extreme heat before are likely better prepared to protect themselves if it happens again, Thompson added.
This report from The Canadian Press was first published on May 4, 2022.