Scientists working for the oil giant Exxon privately “predicted global warming correctly and skillfully” in reports that date back to the late 1970s and early 1980s, a new study shows. Despite this, however, the company publicly cast doubt on climate science and lobbied against climate action, the researchers argued.

Internal documents and research papers had previously established that Exxon was aware of the dangers of global warming from at least the 1970s. However, a new study has made clear that the company’s scientists were very accurate in their projections, predicting a curve of temperature and CO2 emissions close to what actually happened.

The scientists predicted there would be a global warming of about 0.2 degrees Celsius per decade due to the emissions of greenhouse gases from fossil fuels. The new analysis found that Exxon’s science was very accurate and “consistent with, and at least as skillful as, those of independent academic and government models.”

“This paper is the first-ever systematic assessment of a fossil fuel company’s climate projections, the first time we’ve been able to put a number on what they knew,” Geoffrey Supran, lead author, said in a statement. “Excellent scientists within Exxon modeled and predicted global warming with, frankly, shocking skill and accuracy.”

Looking into Exxon’s data

The researchers looked at over 100 internal documents and peer-reviewed scientific publications either done in-house by Exxon scientists or co-authored in independent publications between 1977 and 2014. They found 63-83% of the global warming projections by Exxon’s scientists were consistent with actual temperatures over time.

Exxon correctly dismissed the idea that the world was heading to an imminent ice age, a possibility discussed in the 1970s. The company’s scientists accurately predicted that human-caused climate change would be first detectable in the year 2000, plus or minus five years, and also estimated how much CO2 would lead to dangerous warming

The Earth has warmed a bit more than 1 degree Celsius compared to preindustrial times of the late 1800s. This warming has led to extreme weather events, such as heat waves, flooding, and droughts. The researchers in this new study found, for example, that Exxon’s own climate models anticipated this kind of temperature increase.

Packed with this extensive knowledge, Exxon started a lengthy campaign to downplay or discredit what its own scientists had confirmed. For example, as recently as 2013, Exxon’s former chief executive, Rex Tillerson, said that climate models were “not competent” and that “there are uncertainties” over the impact on the planet of burning fossil fuels.

“I think this new study is the smoking gun, the proof, because it shows the degree of understanding … this really deep, really sophisticated, really skillful understanding that was obscured by what came next,” Naomi Oreskes, study co-author, said in a statement. “ExxonMobil scientists knew about this problem to a shockingly fine degree.”

The company currently faces over 20 lawsuits brought by states and local governments for damages caused by climate change. Baltimore in the US was among the first. Last year, a group of cities in Puerto Rico filed a racketeering lawsuit against fossil fuel companies, including Exxon, claiming they conspired to mislead the public about climate change.

The study was published in the journal Science.