Instead, the suit is a straightforward shareholder fraud case contending that Exxon deceived investors by saying publicly that it had fully accounted for the risks of climate change while in fact deliberately minimizing and, in some cases, ignoring these risks when making its business decisions. These actions, the suit charges, inflated the company’s value by making it appear to be on firmer financial footing than it actually was.

The case is also numbingly complex, involving competing claims about arcane “proxy costs” — theoretical calculations of the expenses the company would be likely to incur when stringent government regulations kick in to limit the emissions of climate-altering compounds. The suit claims that even as Exxon assured investors that it was applying rigid accounting to operations and holdings, in practice it was not, thus avoiding painful write-downs on oil and gas reserves it might have to abandon if the true costs of regulation were taken into account. In one example, the suit charges, the company failed to apply publicly stated proxy costs to 14 oil sands projects in Alberta, leading to undercounting future regulatory expenses by $25 billion.

To all of this, Exxon has two main responses. First, it says, the attorney general misunderstands the way the company calculates and applies costs. Scott Silvestri, an Exxon spokesman, said in a statement, “The company looks forward to refuting these claims as soon as possible and getting this meritless civil lawsuit dismissed.” Second, echoing what the company has said from the beginning, it claims that the inquiry is basically a witch hunt inspired by interest groups and Mr. Schneiderman, a politically ambitious Democrat.