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In an email obtained by the Union of Concerned Scientists (UCS), a former scientific advisor to ExxonMobil, the world's largest oil company, says it was aware of climate change as early as 1981.

The revelation is significant because it shows the company knew of the broad scientific consensus on climate change, yet continued to fund — to the tune of over $30 million — groups that sought to confuse the public on the scientific certainty that the Earth's atmosphere is warming and humans are the primary cause.

UCS's Nancy Cole said the email, written by Leonard Bernstein, a 30-year industry veteran and co-author of the UN Intergovernmental Panel on Climate Change's 2007 synthesis report, provides damning proof that Exxon has known it was harming the planet for much longer than they've admitted.

"[Bernstein's email] moves the date back even further than what we'd known before," Cole told VICE News. "It's one more nail in the coffin, if you will. It's another piece of evidence that gives the public some insight into how long we have been deceived."

UCS discovered the email while conducting research for its recently published report The Climate Deception Dossiers, which chronicles fossil fuel industry-funded efforts to mislead the public about climate change.

Bernstein was asked last year by faculty at Ohio University to comment on corporate ethics, specifically his thoughts on for-profit companies that are not required to pay for the environmental and health consequences of pollution.

In his response, Bernstein said corporations are only interested in environmental impacts if it affects their profits.

"Exxon first got interested in climate change in 1981 because it was seeking to develop the Natuna gas field off Indonesia," Bernstein wrote. "This is an immense reserve of natural gas, but it is 70 percent CO2."

Carbon dioxide (CO2) is the biggest man-made contributor to global warming.

"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," Bernstein wrote. "They were well ahead of the rest of industry in this awareness."

Published this week, the UCS report provides insight into how hard the oil and gas industry has tried to clandestinely spread doubt about human-made climate change since the early 1990's.

For example, a leaked 1998 memo written by the oil and gas trade group American Petroleum Institute — whose oldest member was Exxon, which merged with Mobil in 1999 — explained that "victory" in the climate change debate would be achieved when "recognition of uncertainties [about human-made global warming] becomes part of the 'conventional wisdom.'"

Asked about ExxonMobil's attempts since 1981 to sow uncertainty about anthropological climate change, company spokesman Richard Keil told VICE News it has never denied humanity's potential to impact the climate system.

"We believe the threat of climate change is real and demands action, and we are taking steps to reduce greenhouse gas emissions in our operations, help consumers reduce their emissions, and supporting research and participating in research into further emissions reductions," Keil said.

According to the UCS report, more than half of all industrial carbon emissions ever released into the atmosphere has occurred since 1988, years after Exxon considered the impact of the Natuna gas field.

While Keil would not comment on ExxonMobil's current plans for the project, the Jakarta Post reported last year that the company had a 35 percent participating interest in a business consortium that will begin developing the field in 2020.