Decades of research by scientists at Exxon accurately predicted how much global warming would occur from burning fossil fuels, according to a new study in the journal Science.

The findings clash with an enormously successful campaign that Exxon spearheaded and funded for more than 30 years that cast doubt on human-driven climate change and the science underpinning it. That narrative helped delay federal and international action on climate change, even as the impacts of climate change worsened.

Over the last few years, journalists and researchers revealed that Exxon did in-house research that showed it knew that human-caused climate change is real. The new study looked at Exxon's research and compared it to the warming that has actually happened.

Researchers at Harvard University and the Potsdam Institute for Climate Impact Research analyzed Exxon's climate studies from 1977 to 2003. The researchers show the company, now called ExxonMobil, produced climate research that was at least as accurate as work by independent academics and governments — and occasionally surpassed it.

That's important because ExxonMobil and the broader fossil fuel industry face lawsuits nationwide claiming they misled the public on the harmful effects of their products.

"The bottom line is we found that they were modeling and predicting global warming with, frankly, shocking levels of skill and accuracy, especially for a company that then spent the next couple of decades denying that very climate science," says lead author Geoffrey Supran, who now is an associate professor of environmental science and policy at the University of Miami.

The Earth already has warmed a little more than 1 degree Celsius (about 2 degrees Fahrenheit) compared to preindustrial times of the late 1800s. That warming has led to extreme weather in recent years, including heat waves, droughts and floods. The researchers found, for example, that Exxon's own modeling charted this kind of temperature increase.

"Specifically, what we've done is to actually put a number for the first time on what Exxon knew, which is that the burning of their fossil fuel products would heat the planet by something like 0.2 [degrees] Celsius every single decade," Supran says.

ExxonMobil's response

While ExxonMobil has not addressed the specifics in this paper, the company did respond before the research was published.

"This issue has come up several times in recent years and, in each case, our answer is the same: those who talk about how 'Exxon Knew' are wrong in their conclusions," wrote ExxonMobil spokesman Todd Spitler in a statement.

The campaign to reveal what ExxonMobil knew and when has coalesced on social media under the hashtag #ExxonKnew.

"ExxonMobil's understanding of climate science has developed along with that of the broader scientific community," said Spitler. He said "well intended, internal policy debates" have been recast by some "as an attempted company disinformation campaign."

Spitler pointed to a related 2019 case ExxonMobil won in New York and specifically highlighted a section on Page 37 of the 55-page ruling, in which Justice Barry Ostrager of the New York State Supreme Court wrote:

"What the evidence at trial revealed is that ExxonMobil executives and employees were uniformly committed to rigorously discharging their duties in the most comprehensive and meticulous manner possible. ... The testimony of these witnesses demonstrated that ExxonMobil has a culture of disciplined analysis, planning, accounting, and reporting."

In that case, the New York Attorney General's Office failed to show that the company broke state law and deceived investors by allegedly downplaying the effects climate change would have on ExxonMobil's finances.

As NPR reported at the time, Ostrager also wrote, "Nothing in this opinion is intended to absolve ExxonMobil from responsibility for contributing to climate change through the emission of greenhouse gasses in the production of its fossil fuel products." And Ostranger added, "this is a securities fraud case, not a climate change case."

Research could aid climate lawsuits

ExxonMobil has a lot at stake in arguing that it did not mislead investors or the public about what it knew about the climate-warming effects of fossil fuels, and when.

The company faces more than 20 lawsuits brought by states and local governments for damages caused by climate change. Baltimore was among the first. And last year, cities in Puerto Rico filed a racketeering lawsuit against fossil fuel companies, industry groups and others claiming they conspired to mislead the public about climate change.

This new research could provide more evidence for those cases as they progress through the courts, says Karen Sokol, a law professor at Loyola University in New Orleans.

"What Exxon scientists found and what they communicated to company executives was nothing short of horrifying," says Sokol. Given how science works, she says that should have prompted the company to raise an alarm to the public and policymakers.

"Imagine that world and the different trajectory that consumers, investors and policymakers would have taken when we still had time, versus now when we're entrenched in a fossil fuel-based economy that's getting increasingly expensive and difficult to exit," says Sokol.

She says that provides "significant evidence" of the kind of deception and law-breaking that many of the lawsuits are based on.

ExxonMobil and the broader fossil fuel industry have sought to stop lawsuits by getting states to pass laws to block municipalities from suing, according to the watchdog group Center for Climate Integrity.

The industry also has tried to move the cases to potentially friendlier federal courts, arguing they're of national significance. In August the U.S. Circuit Court of Appeals in Philadelphia declined to do that for a 2020 case brought by the state of Delaware and city of Hoboken, N.J. Delaware sought compensation for lost property value because of climate-induced sea level rise and flooding. Hoboken wants money to pay for current and future costs.

As the largest U.S. oil company, ExxonMobil often faces more scrutiny from activists. The company now says it's "committed to being part of the solution to climate change and the risks it poses." Climate activists are skeptical, but one thing is clear: Questions over the company's history of stalling climate action will be the subject of legal battles for years.