We expect prosecutors to investigate when evidence suggests a corporation may have committed a crime, especially when the company may have harmed the public or deceived investors.

That's why the legal community was surprised that Texas Attorney General Ken Paxton would try to stop an investigation by another attorney general into whether Exxon Mobil Corp. misled the public and investors about climate change.

Paxton's court filing defending Exxon Mobil is not surprising, though, coming from a man bold enough to remain in office while facing state and federal fraud charges. The former corporate lawyer has proved he's a political pawn who could care not less about law enforcement, because there is certainly enough evidence to warrant an investigation into Exxon Mobil.

Seventeen attorneys general, who unlike Paxton have criminal law experience, want to know when Exxon Mobil knew climate change was real, when it realized global warming would hurt its business, and whether it misled shareholders about the potential risk.

Exxon Mobil has denied wrongdoing, claimed freedom of speech as a defense and calls the investigations politically motivated. But Exxon Mobil's internal documents, obtained by investigative journalists, raise serious questions, and Exxon Mobil has not disputed their validity.

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Scientists working for Exxon Mobil in the 1970s and 1980s were among the first to recognize global warming, and that carbon dioxide was a major contributor, according to company papers published online by Inside Climate News and the Los Angeles Times in September 2015.

"There is general scientific agreement that the most likely manner in which mankind is influencing the global climate is through carbon dioxide release from the burning of fossil fuels," Exxon Mobil senior scientist James Black told the company's management committee in 1977. Black told senior managers and scientists the following year that a doubling of the carbon dioxide concentration in the atmosphere would increase average global temperatures by 4 to 5 degrees Fahrenheit and cause significant climactic changes, according to the documents.

The website DeSmog went through the reviews of environmental protection activities produced by Exxon Mobil subsidiary Imperial Oil, which were distributed to company officials worldwide.

"It is assumed that the major contributors of CO2 are the burning of fossil fuels," the 1978-79 edition states. "There is no doubt that increases in fossil fuel usage and decreases of forest cover are aggravating the potential problem of increased CO2 in the atmosphere."

Exxon Mobil managers recognized the threat to the planet and their business model. Exxon Mobil scientists studied atmospheric CO2 and built climate models in the early 1980s. Company scientists worked alongside the world's top climate experts and published academic papers, many of which are the basis for our understanding of climate change today.

A memo from 1980 called on Exxon Mobil managers to promote the company's research into finding a solution to "the Greenhouse Effect."

"It is significant to Exxon since future public decisions aimed at controlling the buildup of atmospheric CO2 could impose limits on fossil fuel combustion," the memo said. "It is significant to all humanity since, although the CO2 Greenhouse Effect is not today widely perceived as a threat, the popular media are giving increased attention to doom-saying theories about dramatic climate changes and melting polar icecaps."

But times were tough for oil companies, and by the late 1980s, Exxon Mobil reduced funding for the research. The company shifted tactics in the 1990s and joined with the American Petroleum Institute to create the Global Climate Science Team, which according to a document obtained by the New York Times, planned to cast doubt on "(a) climate change actually is occurring, or (b) if it is, whether humans really have any influence on it."

While individuals in the United States enjoy free speech, there are limits on how much corporate executives can spin the facts.

Companies cannot intentionally misrepresent their product or its potential for harm, and investigators want to know if Exxon Mobil deliberately lied about the impact of CO2 on the climate to keep selling gasoline and other fuels. Publicly traded corporations must also disclose any risks to the company's future profits in annual reports to the SEC. Exxon Mobil only began mentioning climate change as a regulatory risk in 2010.

Climate activists are behind these investigations and have adopted tactics used by health activists against tobacco companies. That's an imperfect analogy at best, as there could be reasonable explanations for why Exxon Mobil's leadership dismissed their own scientists' findings.

But we know from the tobacco cases that major corporations are capable of committing large-scale fraud on shareholders while inflicting harm on the public.

Prosecutors have a duty to investigate and determine if charges are warranted against Exxon Mobil.

But our attorney general prefers to turn a blind eye, while hoping the public will ignore the fraud allegations against him.