Extreme weather caused by climate change in Quebec this summer made the province a tinderbox for the spark and spread of wildfires, according to a new analysis by an international team of climate scientists aiming to provide a common understanding on the role of climate change in extreme weather.
The World Weather Attribution initiative examined Quebec’s weather conditions across seven days in the summer to find that climate change doubled the likelihood of record-breaking high temperatures, low humidity and the rapid disappearance of snow cover – conditions which fueled wildfires.
The study comes as scientists across the world race to attribute weather to climate change, in hopes that more data will allow us to better predict and fight extreme events such as forest fires moving forward.
The 2023 Canada wildfire season has been the most intense on record, with close to 14 million hectares burned. The season is double the previous 1989 record of 7.9 million hectares. Almost 200,000 people have been evacuated from affected areas and the fires have claimed four lives. Smoke has also led to dangerous air quality conditions in cities across Canada and the U.S.
“This report is a common vision on the problem for everyone,” said Jon Boucher, a Quebec-based research scientist at Canadian Forest Service and one of 16 co-authors on the study. “When we all have a common enemy or a common goal it is easier to get moving.”
In the study, researchers focused on Quebec’s landscape in the run up to the forest fires, using the Fire Weather Index to get a clear picture on the conditions before the fires. This index combines measurements of temperature, wind speed, humidity and precipitation to estimate the risk of wildfire.
To figure out how climate change led to an increase in these risks, they compared the FWI results to pre-industrial levels. They found that the 1.2-degree temperature increase (attributed to global warming) doubled the chances of wildfire risk.
Dr. Boucher pointed out that the study did not prove that climate change caused wildfires but rather showed that climate change led to an increased likelihood of conditions (high temperature, low humidity and little snow cover) that are perfect for wildfires to start. He said the province was unlucky that these dry and hot conditions were matched with lightning storms and little rain.
The study is the latest by World Weather Attribution, an international collaboration that is attempting to draw a line between climate change and extreme weather events, such as storms, extreme rainfall, heatwaves and droughts. They have published 50 studies to date.
This kind of work is important as climate change leads to extreme conditions becoming the norm, said Dr. Kent Moore, an atmospheric physicist who studies climate at the University of Toronto. He was not involved in the study.
In today’s climate, extreme weather conditions can be expected to occur once in every 25 years, meaning they have about a four-per-cent chance of occurring each year. This chance will only increase as the planet warms, according to the press release published by the World Weather Attribution initiative.
But attributing forest fires to climate change is a tricky science, said Dr. Moore. Unlike heatwaves, wildfires are not purely a matter of temperature. They are a combination of numerous factors, from humidity to poor forestry management. Wildfires are also a naturally occurring event.
He noted that the research rests on climate models, which are not a perfect science. For example, an atomic physicist can repeat the same study in a controlled lab environment. Climate scientists only have one system: earth. Unlike a lab, conditions cannot be controlled and outcomes cannot be repeated. We cannot therefore know for sure what an extreme event in the pre-industrialized period would look like.
“The real challenge is how do you unpack the effect of climate change and assess what this event would have looked like had we not pumped CO2 up into the atmosphere,” said Dr. Moore.
Nevertheless, the models are constantly improving and the science remains valid and important, he said.
“Extreme events always happen. The question is how much more extreme are they because of climate change?” said Dr. Moore. “It’s important because it allows us to gauge the impact that climate change has made.”
Dr. Boucher agrees, adding that all climate models need to be continuously updated to account for the rapidly changing weather patterns. For example, this summer’s extreme heat and low humidity in Quebec was an extreme by today’s standards but will be the norm by the end of the century.
He said this is more reason to collect and publish this kind of data. He hopes it will inform public policy, boosting awareness, resources and community planning all with the aim of making communities safer.
“We need to understand the scale of the actual problem,” said Dr. Boucher. “So we can all understand and be on the same page.”