Human-caused climate change made 2023’s severe, months-long fire weather conditions that powered Canada’s record-breaking blazes at least seven times more likely to happen, according to a new scientific analysis published Tuesday. The study by the World Weather Attribution group also found that over the year, fire-prone conditions were 50 percent more intense as a result of global warming, primarily a result of burning fossil fuels. Canada is experiencing its most devastating fire season ever, a result of record high temperatures, low humidity, and early thaw of snowmelt. Nearly 15.3 million hectares (37.8 million acres) have burned: an area larger than Greece, and more than double the previous 1989 record. Some 200,000 people have been evacuated, at least four have died, and smoke from the burning forests has led to dangerous air pollution spreading across much of Canada and the United States to the south. As of late July, the forest fires had directly emitted more than a billion tons of carbon dioxide into the atmosphere as well as methane and nitrous oxide that had a combined greenhouse effect equivalent of a further 110 million tons of carbon dioxide, according to recent research. For the current study, scientists examined the eastern province of Quebec, honing in on zones that are similar in climate and vegetation. The region saw an exceptionally high number of fires in May and June, when national temperature records were smashed by 0.8 degrees Celsius (1.4 degrees Fahrenheit). Because wildfires are highly complex and not driven solely by climate, the researchers focused instead on conditions conducive to blazes, using a metric called the Fire Weather Index (FWI). This combines temperature, wind speed, humidity, and precipitation. The team accumulated this data from January to July to derive a measure of severity of fire weather over the entire season. While Quebec’s fires were unprecedented, analysis of the recent climate record indicated the seasonal conditions causing the blazes are no longer rare, occurring once every 25 years. This means they now have a four percent chance of happening every year. To understand the contribution of man-made global warming, they used computer model simulations to compare the climate as it is today, after about 1.2C (2.2F) of global warming since the late 1800s, with the climate of the past. This showed climate change had made seasons of this severity at least seven times more likely to occur compared to pre-industrial times. The analysis emphasizes the need to reduce greenhouse gas emissions to prevent future severe fire weather conditions. Yan Boulanger, an ecologist with the Canadian Forest Service and the report’s second author, highlighted the cumulative impact of circumstances favorable to fire, stating that the duration of fire weather conditions played a significant role in the size of the fires. The team also found that peak fire weather conditions were more than twice as likely to occur than in the past. The analysis showed that if the world continues burning fossil fuels at high rates, the likelihood and intensity of severe fire weather conditions will only increase. These fires pose a threat to the forestry sector, and it remains uncertain whether regeneration efforts can keep up with losses. Indigenous communities, who made up 75 percent of those evacuated in July, are the most impacted by the fires. The study emphasizes the urgent need to reach net-zero emissions and advocates for changes in political leadership to address climate change effectively.