The research, published in Nature, is the first of its kind to trace a direct, quantifiable economic impact from extreme heat back to the historical emissions of individual companies. It names BHP, Rio Tinto, Santos, Whitehaven Coal, and Woodside Energy as collectively contributing more than US$600bn (A$929bn) in damages linked specifically to heat-driven economic losses between 1991 and 2020.
"This study closes the gap of plausible deniability," said lead author Christopher Callahan of Stanford University. "For decades, companies have argued it's impossible to trace specific climate harms back to specific emitters. That's no longer scientifically credible."
New method, staggering figures
The study builds on historical emissions data and climate modelling to connect the emissions of 111 major fossil fuel producers worldwide — including Chevron, ExxonMobil, BP, Gazprom and Saudi Aramco — with the intensification of extreme heat.
Using economic modelling, the researchers quantified the resulting GDP losses from the hottest five days of each year, finding that the world's largest polluters have collectively caused trillions in damage. Saudi Aramco alone was linked to more than US$2tn in heat-related economic harm.
Applied to Australia, the model produced staggering figures. While not yet tested in court, the data offers a potential framework for assigning liability to companies for climate impacts that were previously seen as too diffuse to litigate.
Legal implications: A turning point?
Australian courts have historically been hesitant to hold companies directly responsible for climate harms due to the difficulty in proving causation. Companies like Santos, when asked to assess the climate risk of their projects, have pushed back on the idea that emissions from a single activity can be clearly linked to specific climate outcomes.
But Callahan said this new research changes that.
"The science has moved forward. There is now a valid, peer-reviewed methodology to trace the fingerprints of specific actors on climate-related economic losses. That could become the foundation for future litigation — not just for heat, but potentially for floods, droughts and sea-level rise," he said.
Although Australia is already the second most active country in the world for climate litigation after the US, most cases remain focused on procedural matters, such as development approvals or disclosure obligations.
If applied more broadly, this research could support larger lawsuits, similar to those now being pursued across the United States. On Friday, Hawaii became the 10th state to sue oil majors for climate deception — a move that was quickly met with a retaliatory lawsuit from the Trump administration.
From uncertainty to accountability
Callahan noted that the fossil fuel industry's long-standing defence — that climate change is a "shared responsibility" too complex to attribute to any one actor — can no longer stand unchallenged.
"It's a fallacy that emissions are too diluted to trace. We've shown the opposite. There is no scientific basis for denying the connection between what a company emits and the damage it causes," he said.
While legal battles may still be years away from a tobacco-style reckoning, Callahan believes the foundations are finally being laid: "There is a long way to go, but the direction is clear. Climate accountability is no longer just an ethical question — it's becoming a quantifiable one."