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It says emissions from some individual companies, including relatively smaller ones and some of Canada's oil and gas producers, would have been enough to make otherwise impossible heat waves statistically possible.

"These results are relevant not only in the scientific community but also for climate policy, litigation and wider efforts concerning corporate accountability," said the study, led by researchers out of ETH Zurich, a top university for earth sciences.

The researchers linked emissions from the group of cement and fossil fuel producers to about half the increase in heat wave intensity connected to human-caused climate change.

The study attributes the entire value chain of fossil fuel emissions to the producers, an approach criticized by industry groups that argue they don't bear responsibility for end-use emissions, such as car exhaust. 

Climate groups suggest that downplays how major oil companies have long known burning fossil fuels could contribute to dangerous climate change and nonetheless continued to expand production and shape demand. 

°µÍø½ûÇø has reached out to the Canadian Association of Petroleum Producers for comment. 

The study published in the leading science journal Nature is being welcomed by some Canadian climate advocates as a way to advance efforts to hold major oil and gas companies responsible to pay for some of the costs of climate change.  

"At some level, we are all collectively responsible for climate change, but at the same time, this type of paper just makes it that much clearer how much more responsible these companies are," said Andrew Gage, a staff lawyer with West Coast °µÍø½ûÇøal Law. 

The nonprofit is campaigning for local governments in British Columbia to pursue a class-action lawsuit against oil and gas producers over the increasing costs they face in adapting to climate change, from fighting severe wildfires to building seawalls. 

"The fact that they are not paying any of the costs associated with the harm, and in fact, they're making record profits selling these products, sort of shows the problems with the way we've tackled this legally and economically until now," Gage said. 

The new study helps to push the boundaries of the emerging field of climate attribution, where sciencists try to draw links between climate change to specific extreme weather events.

Federal climate scientists in Canada, for example, have recently started to publish results of rapid studies measuring how much climate change increased the likelihood of heat waves across the country.  

Earlier this year, a study also published in Nature established ways to link economic losses to high-emitting companies, but the paper published Wednesday takes a new approach by linking specific heat waves to those companies. 

The study looked at heat waves from 2000 to 2023 recorded in a database of international disasters. Researchers combined data on the estimated emissions of 180 companies with a model of Earth's climate to calculate the temperature change that could be attributed to each of those companies. 

They used that to figure out the change in heat wave probability that could be attributed to each company's emissions. 

The deadly 2021 heat wave over British Columbia was an estimated 2.3 degrees hotter because of climate change, the study suggests. 

Emissions assigned to Cenovus Energy, Suncor Energy and Canadian Natural Resources — three of Canada's largest oil producers included in the study — combined to contribute about 0.0073 degrees of that intensity, according to supplementary data published by the authors. 

Registered nurse Kaitlin Bloemberg said she sees "the human face" of the data contained in the report. 

"I think of patients, families, communities who are suffering and dying because of the climate crisis that is driven by the fossil fuel emissions," said Bloemberg, a nurse in Vancouver involved in local climate advocacy.

More than 600 people suffered heat-related deaths and emergency departments saw an increase in patients during the 2021 heat wave when temperatures peaked at over 40 degrees in many parts of B.C. 

In the years since, Bloemberg said the health sector has taken steps to better prepare for future major heat events. 

"It can't just be the health-care system that's responsible for sort of cleaning up this mess or having the burden of climate change mitigation," she said. 

"The responsibility is taken off the industries who are actually causing these events and whose emissions have been linked to these events." 

In Canada's courtrooms, the most high-profile climate cases have largely focused on holding governments accountable to set emissions targets in line with international commitments to keep global warming in check. 

But in the U.S., cases have emerged seeking to hold the fossil fuel industry directly accountable. 

Earlier this year, a Washington state woman filed a wrongful death suit against seven oil and gas companies that she alleged contributed to an extraordinarily hot day that led to her mother's fatal hyperthermia during the 2021 heat wave.

Chevron's lawyer told The Associated Press the woman was politicizing personal tragedy and suggested the court should "add this far-fetched claim to the growing list of meritless climate lawsuits that state and federal courts have already dismissed."

Gage, the B.C. lawyer, said Wednesday's paper was unlikely to immediately trigger similar cases in Canada. 

"The barriers, I think, have been partly political, and the public understanding why this industry can be said to have played a major role in causing these impacts and should be paying some of the costs. And this paper helps with that," he said. 

This report by °µÍø½ûÇø was first published Sept. 10, 2025.