Hot, dry and windy conditions like those that fueled wildfires this year in eastern Canada are now at least twice as likely to occur there than in a world not warmed by humans by burning fossil fuels, a team of researchers said on Tuesday. It provides the first scientific assessment of the role of climate change in the intensification of the country’s fires.
So far this year, fires have destroyed 37 million acres in almost all of Canada’s provinces and territories. This is more than twice the amount of Canadian land burned in any other year on record. Tens of thousands of people – including most residents of Yellowknife, the capital of the Northwest Territories – have fled their homes. The smoke has turned the air toxic 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 grow is shaped by the structure and composition of forests and landscapes. But heat, rain and snow affect the flammability of trees and boughs, which can determine how intense fires are and how difficult they are to put out.
In an analysis released Tuesday, researchers at the World Weather Attribution Initiative estimated that eastern Canada now has a 4 to 5 percent chance, in any given year, of experiencing severe fire hazard conditions as severe or worse than this year’s. They said this possibility is at least twice as likely as it would be in a hypothetical world without climate change due to human activity. And the possibility will increase as countries blanket the planet in more greenhouse gases.
“The risk of fire weather due to climate change is increasing,” said Dorothy Heinrichs, technical advisor at the Red Cross and Red Crescent Climate Center who worked on the analysis. “Dedicated mitigation and adaptation strategies will be needed to reduce the drivers of risk and reduce its impacts on people’s lives, livelihoods and communities.”
The global weather attribution aims to estimate the extent to which human-caused warming, shortly after the occurrence of a heat wave, flood, drought or other extreme weather event, affects the chances of events of this severity. Scientists do this by using computer models of the global climate to compare the real world with a virtual world unchanged by decades of greenhouse gas emissions.
one of First scientific studies To assess humanity’s contribution to a specific climate event, the devastating European heat wave of 2003 was examined. Since then, researchers have studied extreme events of all kinds and expanded their toolkit to attribute them to human-caused changes. World Weather Attribution, founded in 2015, has developed a standardized protocol so that such analyzes can be completed shortly after severe weather has occurred, while people and policymakers are still debating how to recover and rebuild.
When researchers with the group examined deadly bushfires in Australia in late 2019 and early 2020, they found that the exceptional warmth and dryness that preceded the fires were at least 30 per cent more likely to occur there than in a non-warming world.
As is customary at World Weather Attribution, analysis of Canada’s fires is published before it is submitted for academic peer review. Most of the group’s research is subsequently published in peer-reviewed journals.
Their latest analysis focused on northern Quebec, where in June alone the fires burned nine times more land than they did in the previous decade combined. The region’s wetter climate makes it less accustomed to large wildfires from the west of the country.
The researchers looked at the Fire Weather Index, a measure that includes temperature, humidity, wind and precipitation. They estimated that Quebec’s peak fire season, which is a rough measure of how quickly fires can spread, like this year’s, was at least twice as common as it was without global warming. They said a fire season with cumulative intensity like this year, a potential measure of the extent of land burning in total, is seven times more common.
They cautioned that these are conservative estimates. “The real number will be higher, but it’s very difficult to say how much the increase will be,” said Frederic Otto, a climatologist at Imperial College London who also contributed to the analysis.
Fire season in Canada is not over yet and more than 1,000 fires have broken out there this week, most of them out of control. British Columbia is under a state of emergency as fires threaten areas close to cities including Kelowna and Kamloops.
In Quebec, many recently logged forests may be too young to regenerate after the fire goes out, says Victor Danrolles, a forest ecologist with joint appointments at the University of Quebec in Chicoutimi and the University of Quebec in Abitibi-Temiscaming.
Dr Danrolles, who was not involved in the World Weather Attribution analysis, said the group’s findings did not surprise him. in Study 2021He and several colleagues found that climatic variability was the dominant factor behind the amount of land in eastern Canada burned by wildfires between 1850 and 1990. They found that the climate had a greater effect on the population of the area by settlers of European descent, who burned the lands. to clear it for cultivation.
Today, the rising heat and drought appear to be changing the fire patterns again, Dr. Danrolles said.
“If a year like 2023 becomes something that gets repeated every 20 years, the system will be in a whole new era when it comes to fires,” he said. “It’s something that hasn’t been noticed in the last century, probably not in the last 1,000 years.”