Hot, dry and windy conditions like this year’s wildfires are twice as likely to occur in a world where humans aren’t warming by burning fossil fuels, a team of researchers said Tuesday. , provides the first scientific assessment of the role of climate change in fueling the nation’s fires.
So far this year, fires have ravaged 37 million acres across nearly every Canadian province and territory. That’s more than twice the amount of Canadian land burned in any other year on record. Tens of thousands of people have fled their homes, including in Yellowknife, the capital of the Northwest Territories. Smog has poisoned the air in cities south of Atlanta.
Wildfires can be ignited by lightning or human-caused causes such as unattended campfires, downed power lines, and arson. The way fires spread and grow is shaped by the structure and composition of forests and landscapes. But heat, rain and snow affect how flammable trees and brush are, which determines how fiercely the flames burn and how difficult it is to put them out.
In an analysis released Tuesday, researchers with the Global Weather Attribution Initiative estimate that eastern Canada now has a 4 to 5 percent chance, in any given year, of experiencing high fire danger conditions as severe or worse than this year. In a hypothetical world without human-caused climate change, this probability would be at least double, they said. And the probability increases as nations cover the planet with more heat-trapping gases.
“Fire-weather risks are increasing due to climate change,” said Dorothy Heinrich, a technical advisor at the Red Cross’ Red Cross Climate Center, who worked on the analysis.
After a heat wave, flood, drought, or other extreme weather event, global climate attribution aims to assess how human-caused warming has changed the likelihood of events of such severity occurring. Scientists use computer models of the global climate to compare the real world with a hypothetical one that hasn’t been changed by greenhouse gas emissions for decades.
One The first scientific studies To assess humanity’s contribution to a particular weather event, examine the catastrophic 2003 European heat wave. Since then, researchers have studied all kinds of extreme events and expanded the tools to account for human-induced changes. World Weather Attribution, created in 2015, has developed a standardized protocol so such analyzes can be completed quickly after severe weather impacts, while people and policymakers debate how to recover and rebuild.
When researchers with the team studied Australia’s deadly wildfires in late 2019 and early 2020, they calculated that the exceptional heat and dryness that preceded the flames was at least 30 percent greater than would occur in a world without global warming.
As is common for global weather attribution, Canada’s fire analysis is made public before being submitted for academic peer review. Much of the team’s research has since been published in peer-reviewed journals.
Their latest analysis focused on northern Quebec, where fires burned nine times more land in June alone than in the previous decade. The region’s wetter climate makes it less prone to large wildfires than the western part of the country.
The researchers looked at a fire weather index that includes temperature, humidity, wind and precipitation. They estimate that Quebec fire season peak intensity, a rough measure of how quickly fires can spread, is twice as common this year than it would have been without global warming. And a fire season with overall severity like this year’s, a possible measure of how much land is burning overall, is seven times more common, they said.
They cautioned that these are conservative estimates. “The true number will be higher, but it’s very difficult to say how much higher,” said Friedrich Otto, a climate scientist at Imperial College London who contributed to the analysis.
Canada’s fire season is far from over. More than 1,000 fires have been raging there this week, most of them out of control. British Columbia is under a state of emergency due to fire threats to areas near cities including Kelowna and Kamloops.
In Quebec, many recently harvested forests may be too young to regenerate after the flames leave, said Victor Danirolles, a forest ecologist with joint appointments at the University of Quebec in Chicoutimi and the University of Quebec in Abitibi-Témiscamingue.
Dr Danirolles, who was not involved in the World Weather Attribution’s analysis, said the team’s findings did not surprise him. A 2021 studyHe and several colleagues found that climate fluctuations were the main factor behind the amount of land burned by wildfires in eastern Canada between 1850 and 1990. Climate had a greater influence than the population of settlers of European descent who burned the land. It should be cleared for agriculture.
Today, increasing heat and drought appear to be reshaping fire patterns, Dr Danirolles said.
“If a year like 2023 becomes something that recurs every 20 years, the system will be in a whole new era in terms of fire,” he said. “It’s something that hasn’t been noticed in the last century, maybe not in the last millennium.”
