Hot, dry and gusty weather like this year’s wildfires in eastern Canada are at least twice as likely to occur there than in a world warmed by humans without burning fossil fuels, a team of researchers said Tuesday. , the first scientific assessment of the role of climate change in fueling the country’s fires.
Fires have burned 37 million acres so far this year in nearly all of Canada’s provinces and territories. That’s more than double the amount of land burned in Canada in any other year on record. Tens of thousands of people – including much of Yellowknife, the capital of the Northwest Territories – fled their homes. The smog has poisoned the air in cities as far south as Atlanta.
Wildfires can be started by lightning or by human causes such as unattended campfires, downed power lines and arson. The way fires spread and develop depends on the structure and composition of forests and landscapes. But heat, rain and snow affect the flammability of trees and bushes, which can determine how hard a fire burns and how hard it is to extinguish it.
In an analysis released Tuesday, researchers at the World Weather Attribution Initiative estimated that there is a 4% to 5% chance in any given year that eastern Canada will experience high fire risk conditions as severe or worse than this year. That’s at least twice as likely, they say, as in a hypothetical world without anthropogenic climate change. The likelihood will increase as countries blanket the planet with more heat-trapping gases.
“The risk of fire weather due to climate change is increasing,” said Dorothy Heinrich, technical advisor to the Red Cross and Red Crescent Climate Center who worked on the analysis. “Mitigation and dedicated action is needed. Adaptation strategies to reduce risk drivers and their impact on people’s lives, livelihoods and communities.”
The World Weather Attribution seeks to estimate how human-caused warming shortly after a heatwave, flood, drought or other extreme weather event changes the likelihood of such a severe event occurring. Scientists do this by using computer models of the global climate to compare the real world to a hypothetical world that has not been altered by decades of greenhouse gas emissions.
One of the first scientific studies to assess human influence on a specific weather event looked at the devastating 2003 heat wave in Europe. Since then, researchers have studied a variety of extreme events and expanded their toolkit to attribute them to human-caused changes. Founded in 2015, World Weather Attribution has standardized protocols so that such analyzes can be done quickly after severe weather strikes, when people and policymakers are still debating how to recover and rebuild.
When the team’s researchers examined deadly wildfires in Australia in late 2019 and early 2020, they calculated that unusually warm and dry conditions leading up to the fires were at least 30 percent more likely than in a world without global warming .
As is typical for weather attribution around the world, the analysis of the Canadian fires was made public before submission to academic peer review. Much of the group’s research was later published in peer-reviewed journals.
Their latest analysis focused on northern Quebec, where fires in June alone burned nine times as much land as in the past decade combined. The region’s humid climate makes it less prone to large wildfires than the western parts of the country.
The researchers looked at the Fire Weather Index, which includes temperature, humidity, wind and precipitation. They estimate that Quebec’s peak fire season — a rough measure of how quickly fires can spread — like this year’s is at least twice as high as it would be without global warming. Fire seasons with cumulative severity — a potential measure of the total amount of land burned — are seven times more likely than this year’s, they said.
They caution that these are conservative estimates. “The actual number would be higher, but it’s hard to say by how much,” said Friederike Otto, a climate scientist at Imperial College London, who also contributed to the analysis.
Canada’s fire season isn’t over yet. More than 1,000 fires have burned there this week, most of them uncontained. British Columbia has declared a state of emergency as fires threaten areas near the cities of Kelowna and Kamloops.
In Quebec, many of the recently harvested timber The forest may be too young to regrow after the flames die.
Dr Danny Rawls, who was not involved in the analysis of World Weather Attribution, said he was not surprised by the group’s findings. In a 2021 study, he and several colleagues found that climate fluctuations were the dominant factor in the amount of land burned by wildfires in eastern Canada between 1850 and 1990. They found that climate played a bigger role than European-born settlers in the area, who burned land to clear it for agriculture.
Today, rising heat and dryness appear to be changing fire patterns again, Dr Danny Rawls said.
“If a year like 2023 becomes a year that happens every 20 years, then the system will enter a whole new era in terms of fires,” he said. “It’s something that hasn’t been observed in the last century, maybe the last millennium.”
