Human-caused climate change approximately doubled the likelihood of the hot, dry conditions that enabled major wildfires in Canada's Northwest Territories and northwestern Ontario this summer, according to a rapid analysis released Thursday by World Weather Attribution. The findings shift attention from ignition alone to the weather that allowed flames to intensify, spread rapidly and resist suppression across vast northern landscapes.
Researchers compared the observed fire-weather conditions with simulations of a cooler, preindustrial climate. They concluded that warming caused mainly by burning coal, oil and gas made comparable conditions about twice as likely. The international research collaboration examines how climate change alters the probability and intensity of extreme events, although its fast assessments appear before the slower process of formal peer review.
More than 12,950 square kilometres, or 5,000 square miles, burned in the Northwest Territories fires examined by the team. Study authors said lightning provided the initial spark there, while heat and dryness helped the fires grow too intense and fast for crews to control. Fire scientist Jonathan Boucher of the Canadian Forest Service said the evidence points more strongly to a climate-related problem than to forest management alone.
The analysis also covered northwestern Ontario, another region exposed to unusually favourable burning conditions. Canadian fire expert Mike Flannigan, who did not participate in the study, told the Associated Press that lightning-caused fires account for more than 90 percent of the land burned nationally, even though people ignite about half of all Canadian wildfires. That distinction matters because remote lightning fires can expand far from roads and firefighting bases.
Smoke from the fires crossed provincial and international boundaries, degrading air quality in Canadian and United States cities, including New York. The findings arrive amid political criticism from U.S. President Donald Trump, who has blamed Canadian forest management and raised the possibility of punitive action. Canadian and independent scientists responded that management can influence local risk, but cannot remove the broad warming and drying influence of greenhouse-gas emissions.
Canada's government had warned before the season that above-normal summer temperatures were expected across most regions and that climate change was increasing the frequency and intensity of extreme fire weather. The new analysis does not predict how many additional fires will ignite, but it indicates that dangerous background conditions are becoming easier to reach. Researchers said reducing future risk requires both stronger community and forest preparedness and sustained cuts in heat-trapping emissions.
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