In the late 1970s, scientists at Exxon fitted one of the company’s supertankers with state-of-the-art equipment to measure carbon dioxide in the ocean and in the air, an early example of substantial research the oil giant conducted into the science of climate change.

A new study published Thursday in the journal Science found that over the next decades, Exxon’s scientists made remarkably accurate projections of just how much burning fossil fuels would warm the planet. Their projections were as accurate, and sometimes even more so, as those of independent academic and government models.

Yet for years, the oil giant publicly cast doubt on climate science, and cautioned against any drastic move away from burning fossil fuels, the main driver of climate change. Exxon also ran a public relations program — including ads that ran in The New York Times — emphasizing uncertainties in the scientific research on global warming.

Global warming projections “are based on completely unproven climate models, or, more often, on sheer speculation,” Lee Raymond, chief executive of the newly-merged ExxonMobil Corp, said at a company annual meeting in 1999. “We do not now have a sufficient scientific understanding of climate change to make reasonable predictions and/or justify drastic measures,” he wrote in a company brochure the following year.

In a statement Exxon did not address the new study directly but said “those who talk about how ‘Exxon Knew’ are wrong in their conclusions,” referring to a slogan by environmental activists who have accused the company of misleading the public about climate science.

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In the new study, Geoffrey Supran and Naomi Oreskes of Harvard, and Stefan Rahmstorf of the Potsdam Institute, carried out a quantitative analysis of global warming projections made or recorded by Exxon scientists between 1977 and 2003.

Those records, which include internal memos and peer-reviewed papers published with outside academic researchers, make up the largest public collection of global warming projections recorded by a single company, the authors said.

Overall, Exxon’s global warming projections closely tracked subsequent temperature increases of around 0.2 degrees Celsius of global warming per decade, the study found.

The company’s scientists, in fact, excluded the possibility that human-caused global warming was not occurring, the researchers found.