The wildfires which have swept through Canada have been fuelled by the changing climate scientists have warned.

World Weather Attribution has issued its latest research after more than 3 million hectares have burned to date  across Canada prompting a Level 4 National Preparedness response. Although the season began with below-average wildfire activity, prolonged hot, dry weather through July has driven a rapid escalation in fire activity across the country.

“What was particularly remarkable this year was the exceptionally rapid rate at which burned area accumulated over a very short period of time,” the organisation said. “Estimates indicate that approximately 94% of the total area burned occurred during the five weeks between end of June and end of July.”

Scientists from Canada, the US, the Netherlands and the United Kingdom collaborated to assess to what extent human-induced climate change altered the likelihood and intensity of the weather conditions at the time of the fires, and how the conditions will be affected with further warming.

They found the large numbers of simultaneous fires across Canada and their rapid growth under extreme fire weather conditions are stretching available personnel and firefighting resources (e.g. aircraft, equipment) and resulting in extensive impacts to property and public health.

The impacts of wildfires are reaching far beyond the location of the fire itself. Smoke from the fires affected millions of people over hundreds of kilometres.

“Wildfires can cause severe and often delayed health impacts ranging from difficulty breathing to cardiac arrest.” It added. “Compounding vulnerabilities (e.g. preexisting conditions, socioeconomics) and concurrent extreme weather events can increase the likelihood of negative health outcomes.”

To assess the role of human-induced climate change the team combined the observation-based assessments with climate models. In both regions and for both event definitions the climate models show a much smaller increase in likelihood and intensity. Combining models and observations gives an increase in likelihood of about a factor of 5 in the Northwest Territories for DSR7 and a factor 2 for DSR30 and in Ontario of about 2 for both event definitions.

“Canada’s forests are highly susceptible to wildfire because of their natural fuel characteristics and climate conditions,” it added. “As wildfires become more frequent, larger, and more intense, fuel reduction measures become less effective and fires become increasingly difficult to control.

“Sustaining an effective response through the remainder of the fire season will require continued interagency coordination, flexible deployment of personnel and equipment across jurisdictions, and sufficient surge capacity to respond to new large fires without compromising ongoing operations. Adaptation to increasing wildfire risk requires an integrated risk management approach and can include incorporating future fire risk into timber harvest allocations, improving forest resilience after fires occur by diversifying with less flammable tree species, as well as strengthening early warning systems and implementing multi-risk zoning for land use and development planning that can have multiple benefits. Integrating First Nation’s knowledge and experience strengthens risk assessment, preparedness and response.”

The study added: “The last three fire seasons in Canada have been exceptionally severe, with record-breaking burned area and emissions recorded across multiple regions. In 2023, WWA found that the severe start to the fire season in Quebec was made seven times more likely due to human-caused climate change. Since then, a growing body of peer-reviewed research has established that climate change is driving the increasing severity of extreme Canadian fire seasons.”