Now two years later, that professor, Naomi Oreskes, has co-written a study in which she did what Exxon asked and read the documents — about 187 written between 1977 and 2014.

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In a paper published in the journal Environmental Research Letters this week, Oreskes offered a peer-reviewed analysis that reinforced the conclusions of those news reports in InsideClimate News and the Los Angeles Times: that Exxon contradicted the word of its scientists.

“Exxon accused journalists of using deliberately cherry-picked statements,” said Geoffrey Supran, a postdoctoral fellow at Harvard who wrote the study with Oreskes. “But what we find is when we look at all relevant documents, we observe clear trends. We’ve looked at the whole cherry tree.”

Scoring sentences in the trove of documents for the level of doubt about climate change they conveyed, the researchers found that about four-fifths of internal company documents and peer-reviewed studies made public by Exxon acknowledged climate change was real and caused by humans while 81 percent of advertorials published in the New York Times and other newspapers did the opposite and expressed doubt.

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“Let’s face it,” one 1997 newspaper ad from Exxon read. “The science of climate change is too uncertain to mandate a plan of action that could plunge economies into turmoil.” But just a year earlier, an Exxon researcher wrote in a peer-reviewed paper that the “body of statistical evidence … now points towards a discernible human influence on global climate.”

In response, the company insisted its climate communications have been consistent and dismissed the study as another hit job from activists seeking to tarnish its image.

“The study was paid for, written and published by activists leading a five-year campaign against the company,” Exxon said in a statement. “It is inaccurate and preposterous.”

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The new study was partially funded by the Rockefeller Family Fund, which despite being run by some descendants of John D. Rockefeller, founder of Exxon’s forebear Standard Oil, has contributed financial backing to InsideClimate News and the Columbia Journalism School fellowship that produced the Los Angeles Times series.

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In its response to the study, Exxon added that the company’s “statements have been consistent with our understanding of climate science,” pointing to two ads run in the year 2000 in which the company wrote that climate change may pose a “legitimate long-term risk.” Indeed, the Harvard study found that some of the advertorials — 12 percent — acknowledged the human contribution to global warming.

“ExxonMobil argues that a couple of sentences from two documents undercut our peer-reviewed analysis of 187 documents,” Oreskes and Supran wrote in response. “But we did account for those two documents.”

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Shortly after InsideClimate News and the Los Angeles Times published their stories, the attorneys general in New York and other states, as well as the Securities and Exchange Commission, launched investigations into the company’s past communications. Exxon provided its first full-throated endorsement of the notion that the burning of its main products was warming the planet in 2007, and has since gone on to publicly back a carbon-tax proposal.

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The company’s criticism highlights the long-standing pressure scientists studying climate change and similarly controversial topics are under to speak out in favor of public policies despite the risk of eroding their credibility through activism. Supran and Oreskes, who in their 2010 book “Merchants of Doubt,” wrote about the parallels between campaigns against research on the risks of climate change and tobacco smoking, say they are comfortable in that dual role.

“ExxonMobil also accuses us of being ‘activists,’ as though that is something to be ashamed of,” they wrote in a statement. “But we are proud to be activists. As scientists before us have shown, speaking truth to power is a civic duty.”