As early as 1977, one of Exxon’s senior scientists warned a gathering of oilmen of a “general scientific agreement” that the burning of fossil fuels was influencing the climate. A year later, he had updated his assessment, warning that “present thinking holds that man has a time window of five to 10 years before the need for hard decisions regarding changes in energy strategies might become critical.”

In the 1980s, Exxon scientists collaborated with academic and government researchers to build climate models and understand their implications. When one researcher expressed the opinion that the impacts would be “well short of catastrophic,” the director of the Theoretical and Mathematical Sciences Laboratory at Exxon Research responded in a memo, “I think that this statement may be too reassuring.” He said it was “distinctly possible” that the projected warming trend after 2030 “will indeed be catastrophic (at least for a substantial fraction of the earth’s population),” a conclusion that most climate scientists now hold, assuming we continue business as usual.

What did Exxon executives do with this information? Until 1989, they circulated reports summarizing it inside the company. They allowed their scientists to attend academic meetings, to participate in panels, and to publish their findings in peer-reviewed journals — in short, to behave as scientists. And they did acknowledge the “potentially catastrophic events that must be considered.”

Then corporate executives turned about face. As the scientific community began to speak out more strongly, first about the risks of unmitigated climate change and then about the fact that it was underway, Exxon executives and organizations funded by them embarked on a campaign designed to prevent governments from taking meaningful action. These activities continue today.

Exxon (whose spokesman has disputed the Inside Climate News reporting) had a choice. As one of the most profitable companies in the world, Exxon could have acted as a corporate leader, helping to explain to political leaders, to shareholders and institutional investors, and to the public what it knew about climate change. It could have begun to shift its business model, investing in renewables and biofuels or introducing a major research and development initiative in carbon capture. It could have endorsed sensible policies to foster a profitable transition to a 21st-century energy economy.

Instead — like the tobacco industry — Exxon chose the path of disinformation, denial and delay. More damagingly, the company set a model for the rest of the industry. More than 30 years ago, Exxon scientists acknowledged in internal company memos that climate change could be catastrophic. Today, scientists who say the exact same thing are ridiculed in the business community and on the editorial page of The Wall Street Journal.

We have lost precious time as a result: decades during which we could have built a smart electricity grid, fostered efficiency and renewables and generated thousands of jobs in a cleaner, greener economy. There is still time to prevent the worst disruptions of human-driven climate change, but the challenge is now much greater than it needed to be, in no small part because of the choices that Exxon Mobil made.