Australia Weather News

A quarter of heatwaves this century would have been "virtually impossible" without human-caused climate change, according to a new study.

And while it's incredibly difficult to attribute specific disasters to climate change, let alone individual carbon emitters, the study also claims to have done just that — finding carbon emissions from individual companies drastically increased the likelihood of certain heatwaves.

The study, which was published today in Nature, analysed the individual contributions of 180 large fossil fuel and cement producers, and attributed their individual impact to heatwaves from 2000 to 2023.

It found that Australia's 2018 heatwave would have been near impossible to occur without anthropogenic carbon emissions.

Research like it may help people initiate climate litigation cases in the future,ETH Zurich climate scientist and study lead author Yann Quilcaille said. 

"While many companies argue that they are just one actor among many, we demonstrate that their sole contribution is already enough to cause many disasters," he said.

Heatwaves '10,000 times more likely'

Dr Quilcaille and his colleagues calculated how much human-induced climate change contributed to heatwaves that took place over the past 25 years. 

Using a database of disaster events called EM-DAT, the team analysed 217 heatwaves, and found almost all of them — 213 — were made worse by climate change.

"We show that climate change made … heatwaves more likely and more intense, and that this influence rises quickly over time," Dr Quilcaille said. 

"For a quarter of these heatwaves, climate change has made them more than 10,000 times more likely [to occur]."

This can be interpreted as those heatwaves being "virtually impossible" to occur without climate change, according to Dr Quilcaille.

Researchers thenturned to the large fossil fuel and cement producers, which they call "carbon majors", and assessed how much each contributed to the likelihood and intensity of each heatwave.

The team analysed "scope 1" and "scope 3" carbon emissions — which collectively comprise emissions from producing and burning fossil fuels, and making cement.

Emissions from the 180 carbon producers examined in the study made up half of this century's increase in heatwave intensity when compared to heatwaves from 1850–1900.

RankTop 10 carbon producers1Former Soviet Union state fossil fuel and cement production2Chinese state coal production3Saudi Aramco4Gazprom5ExxonMobil6Chevron7National Iranian Oil Company8BP9Shell10Coal India Limited

For large companies and state-run operations in the top 10 — such as BP, Chevron, ExxonMobil and Shell, which operate in Australia and globally — the number of heatwaves they eachmade 10,000 times more likely was closer to 50.

"This study shows that these companies can cause heatwaves with their sole contribution to emissions, and this is consistent with a much larger scientific literature," Dr Quilcaille said.

"Notably, many heatwaves were so unlikely without climate change that the individual contribution of a producer can be sufficient to make this event possible."

BP, Chevron, ExxonMobil and Shell were contacted for comment.

Australia's 2018 heatwave 'virtually impossible'

Three of the 213 heatwaves analysed by the team were reported in Australia. 

Each of them were more likely to occur — and were almost a degree warmer — due to climate change.

Australian heatwavesIncreased likelihood due to climate changeDegrees warmer due to climate changeJanuary 200921 times more likely0.7°CJanuary 20147 times more likely0.7°CDecember 201810,000 times more likely1.2°C

December 2018 was the hottest December on record at the time, and the new study showed the ensuing heatwave would have been "virtually impossible" without anthropogenic climate change. 

CSIRO's chief environmental research scientist Pep Canadell, who was not involved in the research, called the study "a very neat, clean analysis" and "very robust".

"This paper is quite unique because it takes us to the next level analysis of very specific impacts — who is responsible for which emissions … and how those carbon majors are responsible for specific heatwaves."

Dr Canadell suggests that future studies on the topic may even be able to include the impact on human life, economic slowdown or productivity losses. 

"You can see how this can ultimately be linked to litigation."

'Holy grail' for climate litigation

For Jacqueline Peel, a professor of climate law at the University of Melbourne who specialises in corporate climate accountability, these sorts of studies are a "collaborative effort" between scientists and lawyers. 

"We've seen this area of science develop exponentially in the last few years," she said. 

"The holy grail for [this type of] climate litigation is trying to find corporate liability for loss and damage caused by climate change ... this research is helping fill that gap."

The new research is one of a number of studies published in the past few years that have attributed heatwaves and other climate disasters to climate change and large fossil fuel companies.

Such studies are useful for lawyers and claimants to use when arguing the damage caused by heatwaves or other natural disasters because it provides quantifiable numbers, Professor Peel said.

And, she added, it's not just the largest companies that could be open to legal action, but also some of the smaller carbon majors.

"Where [large fossil fuel companies] are involved in litigation, they defend these cases to the nth degree so these would be very hard cases to win," she said. 

"But it's not just the the really big guys for whom this could be relevant, [the study] also swept up some of the smaller … companies." 

According to Professor Peel, successful climate litigation cases could make companies wary about emitting large amounts of carbon. 

"It puts a great big liability figure on these companies' balance sheets — making an economic case to try and change behaviour."

In 2024, global emissions were still rising, and the Earth's "carbon budget" is running out, with experts predicting a 50 per cent chance we will surpass 1.5 degrees of global warming in less than 6 years. 

While climate litigation, specifically claims of damages against companies,has so far been mostly unsuccessful around the world, it may only be a matter of time before the tide turns, Professor Peel said.

"The case theory is that if enough of these are brought before different courts you'll get a 'tobacco litigation' style moment," she said. 

"Once that domino falls, the theory is the rest of them will fall as well, and it'll lead to these very large liability claims."

From heatwaves to wildfires

While heatwaves might be straightforward for researchers and disproportionately deadly compared to other extreme events, they might not be the best option for climate litigation, according to Professor Peel.

"You need to have a group of people that can be identified as victims of a particular event — that can sometimes be really hard with heatwaves," she said.

If the occurrence of fires, cyclones or droughts can be directly linked to emitters, damage caused by those disasters may be easier to litigate than heatwave-related damages.

The team that published the new paper is now focused on extending the work to wildfires and agricultural droughts, as well as quantifying the specific societal impacts of heatwaves and other climate diasters.

"The scientific community has been working for years now towards end-to-end attributions, linking anthropogenic actors to impacts. Not just temperatures, but economic losses, casualties," Dr Quilcaille said.