Fossil fuel giant ExxonMobil “misled the public” about the risks posed by climate change, an analysis of its public and private announcements on the subject by two Harvard University academics has concluded.

While the company’s scientists and senior executive largely accepted the scientific consensus that global warming is real and poses significant risks, it spent thousands of dollars on regular advertorials in The New York Times (NYT) and other newspapers, in which it sought to cast doubt on the science.

In some cases, the firm, led by the current US Secretary of State, Rex Tillerson, from 2006 to 2016, even contradicted itself.

While at the company, Mr Tillerson used an email account with a fake name, “Wayne Tracker”, to discuss climate change and, since becoming a member of the Trump administration, has advised American diplomats to dodge questions about the US withdrawal from the Paris Agreement on climate change.

The researchers pointed out that, as long ago as 1979, an internal ExxonMobil document discussed the “most widely held theory” that burning fossil fuels would cause “a warming of the Earth’s surface” with “dramatic environmental effects before the year 2050”.

As late as 2008, the firm insisted industry guidelines on reducing emissions should not “imply a direct connection between greenhouse gas emissions from the oil and natural gas industry and the phenomenon commonly referred to as climate change”.

If it is proved ExxonMobil deliberately misled investors about the risks posed to its business by the need to stop using fossil fuels, the company could face prosecution.

And attorneys general in 17 US states and territories are currently looking into whether it and other fossil fuel companies breached consumer protection, investor protection or even anti-racketeering laws in relation to climate change.

Writing in the peer-reviewed journal Environmental Research Letters, Professor Naomi Oreskes and Dr Geoffrey Supran said: “Available documents show a discrepancy between what ExxonMobil’s scientists and executives discussed about climate change privately and in academic circles and what it presented to the general public.

“The company’s peer-reviewed, non-peer-reviewed, and internal communications consistently tracked evolving climate science: broadly acknowledging that anthropogenic global warming (AGW) is real, human-caused, serious, and solvable, while identifying reasonable uncertainties that most climate scientists readily acknowledged at that time.

“In contrast, ExxonMobil’s advertorials in the NYT overwhelmingly emphasised only the uncertainties, promoting a narrative inconsistent with the views of most climate scientists, including ExxonMobil’s own.

“In light of these findings, we judge that ExxonMobil’s AGW communications were misleading; we are not in a position to judge whether they violated any laws.”

The risk of “stranded assets” – reserves of oil and gas that will have to stay in the ground if emission targets are to be met – was acknowledged in internal and other documents but not in the advertorials, the researchers noted.

They added that the advertorials’ attempts to sow doubt in the public’s mind was characteristic of a tactic known as the Scientific Certainty Argumentation Method, or “Scam”.

The researchers’ analysis found 81 per cent of the advertorials expressed doubt that climate change was real and caused by humans, with only 12 per cent accepting this was true.

In contrast, 83 per cent of papers in peer-reviewed journals and 80 per cent of internal documents acknowledged that the scientists were correct.

Astonishingly, ExxonMobil took out an advertorial in The New York Times every Thursday between 1972 and 2001 at a cost of about $31,000 (£24,232) each, reaching a readership in the millions. These articles contained “several instances of explicit factual misrepresentation”, the researchers said.

The company’s scientists’ academic papers – described as “highly technical, intellectually inaccessible for laypersons, and of little interest to the general public or policymakers” – were estimated to have had a readership in the hundreds at most.

“Internal documents show that by the early 1980s, ExxonMobil scientists and managers were sufficiently informed about climate science and its prevailing uncertainties to identify AGW as a potential threat to its business interests,” Prof Oreskes and Dr Supran wrote.

“We conclude that ExxonMobil contributed to advancing climate science – by way of its scientists’ academic publications – but promoted doubt about it in advertorials.

“Given this discrepancy, we conclude that ExxonMobil misled the public.”

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The risk of climate change is, according to one of the world’s leading fossil fuel producers, “clear and the risk warrants action”.

“Increasing carbon emissions in the atmosphere are having a warming effect. There is a broad scientific and policy consensus that action must be taken to further quantify and assess the risks,” it says.

“ExxonMobil is taking action by reducing greenhouse gas emissions in its operations, helping consumers reduce their emissions, supporting research that leads to technology breakthroughs and participating in constructive dialogue on policy options.”

On its track record in relation to the science, ExxonMobil says: “We unequivocally reject allegations that ExxonMobil suppressed climate change research contained in media reports that are inaccurate distortions of ExxonMobil’s nearly 40-year history of climate research.

“We understand that climate risks are real. The company has continuously, publicly and openly researched and discussed the risks of climate change, carbon life cycle analysis and emissions reductions.”

It says the firm’s scientists have been “involved in the forefront of climate research” and that it has “long ... informed shareholders and investors on our perception of the business risks associated with climate change”.