Climate change more than doubled the chances of the hot, dry weather that helped fuel the unprecedented wildfire season in eastern Canada that’s driven thousands from their homes and blanketed parts of the U.S. with choking smoke, according to an analysis released Tuesday.
What’s more, human-caused climate change made the fire season in Quebec — from May through July — 50 percent more intense than it otherwise would have been and increased the likelihood of similarly severe fire seasons at least sevenfold, researchers said.
“The biggest takeaway is, this is because of us that we have seen so many fires this year,” due to greenhouse gas emissions, said Yan Boulanger, a research scientist in forest ecology for Natural Resources Canada. He was one of 16 researchers who collaborated on the analysis for World Weather Attribution, an initiative that aims to quickly evaluate the role of climate change in the aftermath of extreme weather events.
Canada is in the middle of its worst wildfire season on record, with more than 5,800 fires burning over 59,000 square miles from one end of the country to the other, according the the Canadian Interagency Forest Fire Centre. In Quebec alone, more than 20,000 square miles has burned so far this year — an area 176 times larger than all of last year.
Though the analysis looked only at a region of Quebec, hot temperatures and drought conditions also were at a record level in the rest of Canada, “and we know that those fire-prone conditions also are increasing in severity, especially out West,” Boulanger said.
Ongoing wildfires have burned dozens of structures in a resort area of British Columbia and prompted authorities to evacuate about 20,000 people from Yellowknife, the capital of the Northwest Territories.
The analysis estimated the peak intensity of the fire weather by looking at real-world observations in a metric called the Fire Weather Index — which estimates wildfire risk by combining temperature, wind speed, humidity and precipitation — averaged over seven days. The researchers then compared that to a world without climate change using multiple computer simulations and historical weather data, a technique widely accepted in the scientific community. They found that the fire-weather conditions this year were twice as likely.
They also assessed the cumulative effect of the weather conditions from January to July, determining that the duration of those conditions was seven times more likely.
Peter Reich, a forest ecologist who wasn’t involved in the analysis, said he was glad researchers didn’t try to prove climate change caused the fires, but instead looked at the probability that the conditions that led to this year’s fire season would have occurred with or without climate change.
“To me, the scariest finding is just the magnitude of the greater likelihood of intense fire weather because of climate change,” said Reich, head of the Institute for Global Change Biology at the University of Michigan and a professor at the University of Minnesota. “It’s not just 10 percent more likely or 20 percent — there’s a 600 percent” greater likelihood.
Although the analysis did a good job of assessing extreme fire weather, it didn’t capture how broadly it affected the entire country, especially in the arid West, which would show an even stronger connection to climate change, said Mike Flannigan, a professor for wildland fire at Thompson Rivers University in British Columbia.
“I’ve never seen such a wide geographical area in Canada on fire at the same time … and fire season is not over yet,” he said.
Reich said the findings likely would apply across the planet because hotter temperatures increase the drying power of the air.
