OTTAWA - This summer’s wildfires in eastern Canada have raged so intensely that smoke from them darkened skies as far away as Portugal. From the outset, scientists said that Canada’s historic wildfire season bore the hallmarks of climate change. Now, a new analysis confirms and quantifies the impact of planet-warming pollution, showing it more than doubled the likelihood of extreme fire weather conditions in eastern Canada.

Canada has experienced its worst wildfire season on record. Blazes have spread across about 15.3 million hectares, an area roughly the size of Bangladesh, and sent smoke streaming to far-flung locales.

Researchers working as part of the World Weather Attribution (WWA) initiative were able to quantify how global warming influenced the fires by using climate models that weren’t just designed to forecast the future impact of climate change, but also to peer into the past. By taking existing weather observations, the researchers were able to model what fire weather looked like prior to the rise in planet-warming emissions and compare it to today. 

Climate change has upped the odds for more extreme wildfires in at least two ways. The first is by increasing temperatures. Hotter weather alone can be enough to increase wildfire activity by drying out grasses and other plants that can fuel more intense wildfires. At the same time, climate change is also shifting rainfall patterns, leading to periods of more extreme rainfall and more extreme drought. Many parts of Canada have experienced both this year. Specifically, the analysis found that the period between May and June was the hottest on record since 1940, which is as far back as fire weather observations included in the research stretch.

The researchers focused on how climate change affected fire weather – that is, the conditions that are conducive to blazes igniting – and not the fires themselves, because wildfires are a mixture of conditions and luck. At least 120 fires in Quebec, for example, were started by lightning strikes when a storm system swept through the area in early June amid unusually hot, dry conditions. Some of those fires are still burning today. 

“We could have had a similar year weather-wise, but without the lightning strikes, the fire season would have been really different,” said Dr Jonathan Boucher, a researcher with the Canadian Forest Service and co-author on the analysis. 

Other research suggests that climate change will also increase the frequency of lightning. 

The new findings have yet to be peer-reviewed because waiting on the process can take years. The goal of WWA is to “answer the question of the role of climate change in the immediate aftermath of an extreme weather event,” said Dr Friederike Otto, a senior lecturer in Climate Science at the Grantham Institute for Climate Change and co-leader of the initiative.

Wildfires are a necessary part of many ecosystems. They help clear out dead organic material like brush and leaves, and many plants and animals depend on the benefits that wildfires can provide. But Canada’s summer of fire could have long-lasting negative impacts on forests, given the intensity and extent of the burn.

It will take scientists time to assess exactly how forests will react to Canada’s worst wildfire season on record – plus, it’s far from over. In the past week, fires forced tens of thousands to evacuate in Yellowknife, the capital of the Northwest Territories, while British Columbia’s provincial government declared a state of emergency amid widespread blazes and evacuations. This summer, at least five have died, including three firefighters and a helicopter pilot helping to suppress the fires. 

The WWA study focused on Quebec, which was especially hard hit this summer. 

“These conditions have given rise to the largest single fire ever documented in southern Quebec at 460,000 hectares,” said Dr Yan Boulanger, a research scientist in forest ecology at Natural Resources Canada. “Between June 1 and June 25, (we) witnessed more land consumed by fire than the cumulative sum of the preceding 20 years.”  

The wildfires aren’t just being made worse by climate change; they’re contributing to the problem as well. Early estimates show greenhouse gas emissions from the blazes will far exceed those of the rest of the country’s fossil fuel-driven economy. BLOOMBERG