Exxon understood the reality of human-caused climate change decades ago, then spent years publicly manufacturing doubt about it
Where the evidence lands: SupportedThat Exxon (and later ExxonMobil) knew from its own scientists, as early as the late 1970s and 1980s, that carbon dioxide from burning fossil fuels was warming the planet and posed grave risks; that its in-house projections of that warming were accurate; that the company nonetheless spent the following decades publicly manufacturing doubt about climate science through paid 'advertorials' and the funding of denial and lobbying groups such as the Global Climate Coalition; and that this contradiction between private knowledge and public messaging is documented in the company's own records and in peer-reviewed analysis.
Believed by: Broadly accepted as established by climate scientists, historians of science, investigative journalists, and a wave of state and municipal litigators; disputed chiefly by ExxonMobil itself and allied commentators, who contest the framing and the legal conclusions rather than the underlying documents
The full story
What Exxon knew, and when it knew it
In July 1977, a senior Exxon scientist named James Blackstood before the company's management committee with a sobering message. There was, he said, general scientific agreement that the most likely way humanity was altering the global climate was through carbon dioxide released by burning fossil fuels. A year later he refined the warning: doubling the concentration of CO2 in the atmosphere would raise average global temperatures by roughly two to three degrees Celsius, an estimate that sits comfortably within today's scientific consensus.
Exxon did not ignore its own scientist. It did the opposite. The company launched an ambitious in-house research program, fitting its supertanker the Esso Atlantic with instruments to sample atmospheric and oceanic CO2 and building a team to model where the warming was headed. For roughly a decade, Exxon ran one of the more serious corporate climate science efforts of its era, and its findings tracked the emerging mainstream: fossil-fuel combustion was warming the planet, and the consequences could be grave.
That is the documented starting point, and it is not a matter of interpretation. It comes from Exxon's own memos and reports, including a 1982 internal primer marked not for public distribution, unearthed by journalists and later analyzed by academics. The question the rest of this file turns on is not whether Exxon understood the science. It is what the company chose to tell the public once it did.
How the story broke
The phrase “Exxon Knew” entered wide circulation in 2015, through two investigations that arrived within weeks of each other. InsideClimate News published an eight-month project, Exxon: The Road Not Taken, built on hundreds of pages of internal documents and interviews with former Exxon employees, scientists, and federal officials. Around the same time, the Los Angeles Times, working with the Energy and Environmental Reporting Project at Columbia University's Graduate School of Journalism, ran its own series, What Exxon Knew.
The reporting laid out a striking arc. Exxon had understood the problem early, studied it seriously, and then, toward the end of the 1980s, wound down its climate research and turned its energy toward contesting the science in public. The company disputed the coverage and objected in particular to the Columbia reporting, but the internal documents the investigations rested on were largely Exxon's own.
What the journalism established as narrative, academic work would soon test with method. The value of that second step is that it moved the case from “reporters say so” to peer-reviewed analysis of the company's full documentary record, and it is what separates this file from a simple accusation.
The gap between the memo and the ad
In 2017, Harvard researchers Geoffrey Supran and Naomi Oreskes published a content analysis in Environmental Research Lettersthat put numbers to the contradiction. They examined 187 Exxon climate communications spanning 1977 to 2014, sorting each by whether it treated climate change as real, human-caused, serious, and solvable. The pattern was consistent and damning: the company's internal reports and peer-reviewed papers largely acknowledged the science, while its paid, editorial-style “advertorials” in The New York Times, running from 1989 to 2004, overwhelmingly emphasized doubt.
In its own labs the science was settled enough to plan around. On the op-ed page it was uncertain enough to do nothing about.
This is the core of the case, and it is worth stating precisely. The charge is not that Exxon failed to know. It is that the company held two positions at once: a private one, grounded in its scientists' work, that human-caused warming was real; and a public one, sold to readers and policymakers, that the science was too uncertain to act on. A 2020 addendum drawing on further documents reinforced the finding, and Exxon funded outside groups, among them the Global Climate Coalition it helped found in 1989, that carried the same uncertainty message into the political arena.
Then came the sharpest turn of all. In 2023, Supran, Stefan Rahmstorf, and Oreskes reported in Sciencethat Exxon's own global-warming projections, modeled between 1977 and 2003, had been accurate: about 0.20 degrees Celsius of warming per decade, matching later observations and at least as skillful as the academic and government models of the day. The company had not just known the general shape of the problem. Its scientists had gotten the math right.
What the record does not settle
Because the documented core is so strong, it is worth being disciplined about where the case stops. Two temptations lead past the evidence, and resisting them makes the finding more credible, not less.
The first is to treat the courts as having ratified the story. They have not, at least not uniformly. When New York's attorney general took Exxon to trial over allegedly misleading investors about climate risk, Justice Barry Ostragerruled for Exxon in December 2019, finding the state had failed to prove any material misrepresentation. That was a securities-fraud case with a specific burden, not a referendum on “Exxon Knew”, but it is a real loss for the litigants, and any honest account has to include it. Other suits, including Massachusetts Attorney General Maura Healey's case and actions by cities and states, are still working through the courts. Their allegations are allegations, and this file attributes them as such.
The second temptation is to assert that Exxon's doubt-casting single-handedly stalled climate policy. The messaging is documented and the funding is documented, but isolating their precise causal effect on decades of public opinion and legislation is genuinely hard, and the record does not deliver a clean measurement. That climate action was delayed is clear; assigning a specific share of the blame to one company's advertisements is a further step the evidence does not cleanly support.
Exxon, for its part, contests the framing rather than the underlying files. It argues its statements have been cherry-picked and its research mischaracterized, and it published a formal comment challenging the 2017 study. The documents themselves are not seriously in dispute; how to read them still is, at least according to the company.
Why the case lands so hard
“Exxon Knew” stuck partly because it fits a pattern the public has already been taught to recognize. The tobacco industry demonstrably funded science to obscure the harms of smoking, lead and chemical firms did similar, and the manufactured-doubt playbook is now a familiar object of study. An oil-industry version of the same maneuver does not sound outlandish; it sounds expected, and that familiarity primes people to believe the fullest version fast.
It also carries a moral clarity that most corporate scandals lack. A company that understood, from its own scientists, a risk to the whole planet and to its own business, and that chose to sow public doubt anyway, is a story about knowledge and responsibility that needs no embellishment to sting. The peer-reviewed confirmation that Exxon's projections were accurate only sharpened the point: this was not a company that guessed wrong, but one that guessed right and said otherwise in its ads.
The discipline the case demands is to hold that documented contradiction at full strength while declining to overreach into the parts still being fought in court. The private knowledge and the public doubt-casting are established. Whether they add up to fraud, and how much they cost the climate, are questions being litigated and studied, and the honesty of the file depends on keeping the two apart.
Where the evidence lands
On the rated claim, that Exxon knew internally what its scientists had found and publicly manufactured doubt about it, the verdict is substantiated. It rests on the company's own documents, on the 2015 investigations that surfaced them, and on two peer-reviewed studies: the 2017 analysis showing the gap between Exxon's internal acknowledgment and its public doubt, and the 2023 study showing its projections were accurate all along. This is not a contested reading of ambiguous material. It is the convergent conclusion of journalism and academic science working from the same records.
The knowledge is proven. The doubt-casting is proven. What is still being argued is what a court should do about it.
The caveat that protects the finding is the legal one. Some cases against Exxon have failed, notably New York's in 2019, and others continue, their allegations unresolved. Those courtroom outcomes do not change the documentary record, and the record is what earns the verdict. The company understood the science, its own projections were right, and it spent years telling the public the matter was in doubt. That much is substantiated. The rest is being decided elsewhere.
What's still unexplained
- How much Exxon's doubt-casting actually delayed climate policy is genuinely hard to isolate. The advertorials and denial funding are documented, but quantifying their causal effect on public opinion or on specific legislation is a separate and unresolved question from the fact that the messaging happened.
- The legal exposure is unsettled. Exxon won New York's 2019 securities-fraud case outright, while suits by Massachusetts and various municipalities continue. Whether the documented conduct amounts to actionable fraud or consumer deception is a question for courts that have so far reached different results, and this file does not prejudge them.
- Exxon disputes the framing rather than the documents. The company argues its statements have been quoted selectively and its research mischaracterized, and it published a formal comment challenging the 2017 study. The underlying records are not in serious doubt, but the interpretation continues to be contested by the company itself.
Point by point
The claim: Exxon's own scientists told the company decades ago that fossil fuels were warming the planet.
What the record shows: Documented in Exxon's internal records. In 1977 senior scientist James Black briefed the management committee that burning fossil fuels was the most likely driver of climate change, and in 1978 he estimated that doubling CO2 would warm the planet by roughly two to three degrees Celsius, a figure close to the modern consensus. Internal memos and a 1982 primer reviewed by InsideClimate News and the Los Angeles Times show the company's technical staff treating human-caused warming as real and consequential well before it was a public controversy.
The claim: Exxon's in-house climate projections were not just present but accurate.
What the record shows: Confirmed by peer-reviewed analysis. The 2023 Science paper by Supran, Rahmstorf, and Oreskes evaluated the warming projections that Exxon and ExxonMobil scientists produced and modeled between 1977 and 2003. It found most of them accurately forecast warming of about 0.20 degrees Celsius per decade, matching later observations, and that their models were at least as skillful as contemporaneous academic and government models. The company's scientists also correctly rejected a coming ice age and reasonably estimated the carbon budget for limiting warming to two degrees.
The claim: The company publicly cast doubt on the very science it privately accepted.
What the record shows: This is the crux, and it is documented in the 2017 Environmental Research Letters study. Supran and Oreskes analyzed 187 climate communications and found a systematic split: Exxon's internal reports and peer-reviewed papers largely acknowledged that climate change was real and human-caused, while its paid advertorials in The New York Times, running from 1989 to 2004, overwhelmingly emphasized doubt and uncertainty. A 2020 addendum, drawing on additional documents, reinforced the finding. The discrepancy between private knowledge and public messaging is the substantiated core of 'Exxon Knew'.
The claim: Exxon funded organized efforts to manufacture doubt about climate science.
What the record shows: Established through funding records and reporting. Exxon was a founding member of the Global Climate Coalition, an industry group that stressed scientific uncertainty and campaigned against climate agreements through the 1990s. Analyses by groups including the Union of Concerned Scientists and Greenpeace document tens of millions of dollars Exxon channeled over the years to think tanks and advocacy organizations that disputed mainstream climate science. The company later said it had ended funding to some such groups, but the historical pattern is well recorded.
The claim: The courts have already found Exxon guilty of climate fraud.
What the record shows: Not established, and this is where the legal picture must be kept separate from the documented conduct. New York's attorney general sued Exxon for allegedly misleading investors about climate risk, and in December 2019 Justice Barry Ostrager of the New York Supreme Court ruled for Exxon, finding the state had not proven material misrepresentation. Other suits, including Massachusetts Attorney General Maura Healey's consumer- and investor-protection case and actions by cities and states, remain in progress. Those cases advance allegations that courts have not resolved; the 'Exxon Knew' finding this file rates as substantiated rests on the documents and peer-reviewed studies, not on any lawsuit's outcome.
Timeline
- 1977Exxon senior scientist James Black tells the company's management committee that there is broad scientific agreement that the most likely way humanity is influencing global climate is through carbon dioxide released by burning fossil fuels. A year later he warns that doubling atmospheric CO2 would raise average global temperatures by roughly two to three degrees Celsius.
- 1979–1982Exxon launches an ambitious internal research program, including CO2 sampling instruments aboard its supertanker the Esso Atlantic and rigorous climate modeling. Company scientists assemble a body of work confirming that fossil-fuel combustion is driving measurable warming and estimating its likely pace.
- 1982An internal Exxon primer summarizes the state of the science for management, projecting warming broadly consistent with the outside scientific consensus and noting potentially serious consequences. The document is marked not for public distribution.
- Late 1980sExxon winds down its in-house CO2 research. As climate change gains political salience after NASA scientist James Hansen's 1988 congressional testimony, the company shifts posture from studying the problem to contesting it publicly.
- 1989Exxon becomes a founding member of the Global Climate Coalition, an industry group that spent the following decade emphasizing scientific uncertainty and lobbying against measures such as the Kyoto Protocol. The company also begins funding an array of think tanks and advocacy groups that dispute mainstream climate science.
- 1989–2004ExxonMobil runs paid, editorial-style 'advertorials' in The New York Times. A later content analysis finds that these overwhelmingly expressed doubt about whether climate change was real, human-caused, serious, and solvable, in contrast to the company's own internal and peer-reviewed documents.
- 2015InsideClimate News publishes 'Exxon: The Road Not Taken', and the Los Angeles Times runs 'What Exxon Knew' with Columbia University's Graduate School of Journalism. Built on internal documents and interviews with former employees, the investigations establish the gap between Exxon's early knowledge and its later public messaging, and the phrase 'Exxon Knew' enters wide circulation.
- 2017Geoffrey Supran and Naomi Oreskes of Harvard publish a peer-reviewed content analysis in Environmental Research Letters comparing 187 Exxon climate communications, concluding that the company's advertorials misled the public even as its internal and academic documents acknowledged the science.
- 2023Supran, Stefan Rahmstorf, and Oreskes publish in Science a quantitative assessment finding that global-warming projections modeled by Exxon and ExxonMobil scientists from 1977 to 2003 were accurate and skillful, forecasting about 0.20 degrees Celsius of warming per decade, consistent with subsequent observations.
From the case file
The actual records: declassified, released, or leaked. We link straight to each document in its official archive, so you never have to take our word for it. Read the originals yourself.
Supported. Two things are documented, and together they are the case. First, Exxon's own scientists understood by the late 1970s and early 1980s that burning fossil fuels was warming the planet, and their in-house projections of that warming turned out to be accurate: a 2023 peer-reviewed analysis in Science found Exxon's 1977–2003 modeling forecast roughly 0.20 degrees Celsius of warming per decade, on par with independent academic and government models and with what has since been observed. Second, a 2017 study in Environmental Research Letters showed that while Exxon's internal and peer-reviewed documents acknowledged the science, its paid newspaper 'advertorials' overwhelmingly expressed doubt about it. The internal knowledge and the public doubt-casting are both established in the record. What is not settled here, and is deliberately kept separate, is the outcome of specific lawsuits: some, like New York's 2019 securities-fraud case, Exxon won outright, while others brought by states and cities remain in progress. Rated substantiated for the documented conduct, with the contested legal claims attributed to the plaintiffs who make them.
Reviewed by The Conspiratory Editors · Last reviewed July 20, 2026 · How we rate
Sources
- 1.Exxon: The Road Not Taken, InsideClimate News (2015)
- 2.Exxon's Own Research Confirmed Fossil Fuels' Role in Global Warming Decades Ago, Neela Banerjee, Lisa Song and David Hasemyer, InsideClimate News (2015)
- 3.Assessing ExxonMobil's climate change communications (1977–2014), Geoffrey Supran and Naomi Oreskes, Environmental Research Letters (2017)
- 4.Assessing ExxonMobil's global warming projections, G. Supran, S. Rahmstorf and N. Oreskes, Science (2023)
- 5.What Exxon Knew, Columbia Magazine, Columbia University (2016)
- 6.ExxonMobil climate change denial, Wikipedia
- 7.Exxon Knew about Climate Change Almost 40 Years Ago, Shannon Hall, Scientific American (2015)
- 8.Exxon Wins New York Climate Change Fraud Case, Jeff Brady, NPR (2019)
- 9.Exxon's Climate Denial History: A Timeline, Greenpeace USA
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