In 1968, a pair of scientists from Stanford Research Institute wrote a report for the American Petroleum Institute, a trade association for America's oil and natural gas industry. They warned that "man is now engaged in a vast geophysical experiment with his environment, the earth" -- one that "may be the cause of serious world-wide environmental changes."

The scientists went on: "If the Earth’s temperature increases significantly, a number of events might be expected to occur including the melting of the Antarctic ice cap, a rise in sea levels, warming of the oceans and an increase in photosynthesis."

That 48-year-old report, which accurately foreshadowed what's now happening, is among a trove of public documents uncovered and released Wednesday by the Washington-based Center for International Environmental Law. Taken together, documents that the organization has assembled show that oil executives were well aware of the serious climate risks associated with carbon dioxide emissions decades earlier than previously documented -- and they covered it up.

Carroll Muffett, the center's president, told The Huffington Post the documents not only reveal that the industry, including Humble Oil (now Exxon Mobil), was "clearly on notice" about the potential role of fossil fuels in CO2 emissions no later than 1957, but was "shaping science to shape public opinion" even earlier, in the 1940s.

"This story is older and it is bigger than I think has been appreciated before," Muffett said.

ROGER HARRIS via Getty Images

The Center for International Environmental Law, or CIEL, a nonprofit legal organization, said it traced the industry's coordinated, decades-long cover-up back to a 1946 meeting in Los Angeles by combing through scientific articles, industry histories and other documents.

It was during that meeting that the oil executives decided to form a group -- the Smoke and Fumes Committee -- to "fund scientific research into smog and other air pollution issues and, significantly, use that research to inform and shape public opinion about environmental issues," CIEL says on a new website devoted to the documents.

That research, CIEL says, was used to "promote public skepticism of environmental science and environmental regulations the industry considered hasty, costly, and potentially unnecessary."

Muffett said in a statement that the documents "add to the growing body of evidence that the oil industry worked to actively undermine public confidence in climate science and in the need for climate action even as its own knowledge of climate risks was growing."

Last year, InsideClimate News revealed that top executives at Exxon knew about the role of fossil fuels in global warming as early as 1977, then lobbied against efforts to cut greenhouse gas emissions. In January, the New York attorney general announced an investigation into ExxonMobil over allegations that it lied to the public and its investors about climate change.

A report that surfaced in February revealed the American Petroleum Institute knew about climate change in the early 1980s.

The industry group did not respond to HuffPost's requests for comment Wednesday.

CIEL's new documents, however, show that the cover-up has endured for a generation or more.

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Muffett said any document, viewed in isolation, has an element of plausible deniability. "But when you put all of the pieces to the story out there and see how they link, the zone of plausible deniability shrinks, and it shrinks substantially," he said.

The new trove adds to a "robust body of evidence" available to the public showing what the industry knew, when, and what it did with that information, Muffett said.

"Once the companies learned this information, once they were aware of it, they can't unlearn it," he said. "This becomes the baseline."

Muffett said the evidence warrants further investigation. CIEL plans to release additional documents in the near future.

“Oil companies had an early opportunity to acknowledge climate science and climate risks, and to enable consumers to make informed choices," Muffett said in a statement. "They chose a different path. The public deserves to know why."

Attorney Sharon Y. Eubanks, former lead counsel for the Justice Department in federal tobacco litigation, was among those who applauded CIEL for making the documents public.

"Just as was the case with the release through litigation of tobacco industry documents, these documents will shed light on the actions and inactions of a powerful and influential industry," Eubanks said in a statement.