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New York’s attorney general sued Exxon Mobil on Wednesday, claiming the company defrauded shareholders by downplaying the expected risks of climate change to its business.

The litigation, which follows more than three years of investigation, represents the most significant legal effort yet to establish that a fossil fuel company misled the public on climate change and to hold it responsible. Not only does it pose a financial threat to Exxon that could run into the hundreds of millions of dollars or more, but it could also strike a blow to the reputation of a company that has worked to rehabilitate its image, framing itself as a leader on global warming.

The suit does not charge Exxon with playing a role in creating climate change, though the burning of fossil fuels is a major contributor to human-driven warming. Rather, it is a fairly straightforward shareholder fraud suit, the kind that New York attorneys general have long brought and successfully prosecuted under state law.

It says the company engaged in a “longstanding fraudulent scheme” to deceive investors, analysts and underwriters “concerning the company’s management of the risks posed to its business by climate change regulation.”