A Harvard University peer-reviewed analysis has concluded that ExxonMobil Corp. misled the public regarding climate change communications over a 40-year period.

The study, published Wednesday in Environmental Research Letters, involved an extensive review of the company’s scientific research, internal company memos and paid advertisements. Eighty-three percent of ExxonMobil scientist peer-reviewed papers and 80% of internal communications acknowledged climate science.

Meanwhile, only 12% of company advertisements acknowledged climate science and 81% doubted the role of human activity in the changing climate, said researchers Geoffrey Supran and Naomi Oreskes.

"We conclude that ExxonMobil misled the public," the researchers said. "We stress that the question is not whether ExxonMobil 'suppressed climate change research,' but rather how they communicated about it."

The study comes as ExxonMobil is fighting a multi-state lawsuit led by New York that is seeking decades of the company’s internal documents and communications related to climate change. New York Attorney General Eric Schneiderman is leading the investigation, which was begun in 2015.

The Harvard researchers, who specialize in scientific inquiry, analyzed ExxonMobil’s external and internal statements between 1977 through 2014.

Their study, supported by Harvard University Faculty Development Funds and the Rockefeller Family Fund, said "textual analysis is inherently subjective" but overall trends were "clear." The Rockefeller Family Fund last year said it would divest from fossil fuels and eliminate holdings in ExxonMobil, whose predecessor, Standard Oil Co. Inc., was founded in 1870 by John D. Rockefeller Sr.

In response to the study, ExxonMobil said the Rockefeller Family Fund backed previous efforts to show the company apparently had misled on climate issues. ExxonMobil for years has publicly sided with the scientific consensus that human activity has raised greenhouse gas emissions, considered a major cause of climate change. The No. 1 producer also supports a carbon tax on emissions.

“The study was paid for, written and published by activists leading a five-year campaign against the company,” an ExxonMobil spokesperson said. “It is inaccurate and preposterous. Rather than pursuing solutions to address the risk of climate change, these activists, along with trial lawyers, have acknowledged a goal of extracting money from our shareholders and attacking the company’s reputation.”