Climate change made weather conditions that powered Quebec fires twice as likely, scientists say

The record-setting wildfires that ripped through Quebec this summer were made more likely and more intense by human-caused climate change, according to a new analysis by an international team of scientists.

The World Weather Attribution initiative, a U.K.-based group that estimates the contribution of climate change to individual weather events, found that our changing climate made the weather conditions that drove the wildfires two times more likely.

The study focused on Quebec, which experienced an exceptionally high number of wildfires in May and June after a dry, hot spring. The province has recorded a total of 5.2 million hectares burned this year.

Yan Boulanger, a research scientist at Natural Resources Canada and one of the study's authors, called the findings "shocking."

"We know that those extreme fire-prone weather conditions are occurring more frequently," he said in an interview.

"Now we are able to put the number or an estimate on to what extent those conditions that we have seen this year are caused actually by climate change — and the numbers are very high."

Powerful fires likely to occur more often

Quebec was chosen for study because of its particularly difficult season, the researchers said, though other Canadian provinces and territories have also had exceptional wildfire seasons. The researchers said they may also examine a broader region of the country in future.

Across Canada, an estimated 15.3 million hectares have burned already this season — more than twice the previous record of 7.6 million reported in 1989.

The Quebec study has not yet been subject to scientific peer review, but it is based on peer-reviewed modelling. In the past, the research group has subjected their studies to review and have not had to change their findings.

In this case, Boulanger and the other researchers used models to simulate how weather systems might behave without climate change, and compared those with what is happening today.

The study used the Fire Weather Index (FWI), a metric that combines temperature, wind speed, humidity and precipitation in order to estimate the risk of wildfire.

The researchers analyzed the seven-day maximum of the FWI over the study region — which spans much of central and northern Quebec — to assess the peak intensity of the fire weather. They concluded that the fire weather in Quebec was twice as likely to occur and around 20 per cent more intense because of climate change.

The researchers also noted that while the fire-prone weather conditions were unprecedented, they are expected to become less and less unusual.

In today's climate, similar weather conditions can be expected to occur once every 25 years, the researchers said, meaning that they have about a four per cent chance of occurring each year.

But if the planet continues to warm, the risk of even greater wildfires will further increase, Boulanger said.

"The odds of having more of these kinds of events are increasing into the future."

Rise of attribution science

The study was conducted by 16 researchers within the World Weather Attribution group, from universities and meteorological agencies in Canada, the Netherlands, the U.K. and the U.S.

Founded in 2015, the group studies extreme weather events, such as droughts, floods and heat waves to assess the role played by climate change. It is part of the growing field of attribution science, which attempts to make connections between individual weather events and climate change.

Such studies can serve an important role in shaping public policy, said Friederike Otto, a climate scientist at the Imperial College of London who was also involved in the study.

"There are often important lessons that can be used for the next time such an event occurs," she said.

A satellite image from June shows smoke Quebec's wildfires, centre, and Ontario, left, drifting southward. (CIRA/NOAA/The Associated Press)

That's a sentiment echoed by Mohammad Reza Alizadeh, a climate data scientist at McGill University in Montreal who was not involved with the research.

We're entering a "new chapter" in our understanding of climate events, he said, also pointing to Australia's 2019-20 bushfire season, California's unprecedented 2021 wildfire season and the persistent heat waves that have swept through Europe for the past two summers.

"All these kinds of events, they are giving us a wake-up call," said Alizadeh. "To say we really need to … maybe reconsider our definition of extreme events.

"We really need to adapt and update our adaptation plans, our definitions … and also even our studies and science."