For 30 years, Lenny Bernstein was the climate expert at the oil giant Exxon-Mobil. Through the years, he watched Exxon funnel up to $30 million to climate change deniers. He watched the company dismiss the Rockefellers, Exxon’s founders, as they urged the company to accept climate change and switch to clean energy. Now, in light of an email penned by Bernstein himself, it’s been revealed that Exxon knew that climate change was real all along — and was confident that the government would eventually regulate carbon dioxide emissions.

Bernstein wrote the revealing email in response to a message from Alyssa Bernstein, the director at the Institute for Applied and Professional Ethics at Ohio University, asking him for ideas to present to students for discussions on ethics.

Exxon knew about climate change as early as 1981, according to the email — at least seven years before climate change became much of a public issue. It was when the company was deciding whether to develop the Natuna gas field, a huge natural gas deposit in Southeast Asia, that it seriously began factoring climate change into its plans. Exxon knew that Natuna’s reserves were made up of 70% carbon dioxide, and they understood that releasing this into the atmosphere would someday have its consequences. At the time, releasing Natuna’s gases into the air would have accounted for 1 percent of projected global carbon dioxide emissions.

Exxon didn’t end up developing Natuna, for reasons the company hasn’t disclosed. What it did do, however, was fund climate change deniers for the next 27 years, even as it factored climate change regulations into its business plan.

“Corporations are interested in environmental impacts only to the extent that they affect profits, either current or future,” Bernstein wrote in the email. “In the 1980s, Exxon needed to understand the potential for concerns about climate change to lead to regulation that would affect Natuna and other potential projects.”

In an interview with The Guardian, a spokesman for Exxon, Richard Keil, denied that the company funded climate change deniers, and said the company has factored the probability of carbon taxing into its business plans since 2007.

Exxon’s short-term play worked: There was a long delay between 1981 and meaningful carbon regulation. But the reason we have meaningful carbon regulation is to preserve life and civilization on the planet Earth. Where all its customers live. Where all its shareholders live, even. It publicly denied truths that could’ve delayed the apocalypse. Brilliant business plan, guys. Let us know how that worked out for you once Florida is knee-deep under saltwater, New York follows Atlantis, and California wilts for lack of rain.

You can read the whole email here.