Oil behemoth Exxon Mobil Corporation (XON  ) has been accused of misleading investors about the true cost of climate change its operations have yielded by having two sets of books, in a New York lawsuit.

Exxon has been accused of defrauding investors out of up to $1.6 billion, by only alerting them to a single set of underlying assumptions used in financial statements, that masked, to a large extent the true environmental impact of drilling.

More specifically, the lawsuit claims Exxon falsely informed investors it had properly evaluated the impact of future climate regulations on its business using a "proxy cost" of up to $80 per ton of carbon emissions, but internally used a divergent set of numbers as low as $40 per ton or none at all. This has also caused investors to overvalue the company's stock.

"If companies like Exxon accurately account for the necessary degree of regulation to prevent even more dangerous global warming from happening, it will make less and less sense to continue to invest in developing fossil fuel projects," said Michael Burger, executive director of the Sabin Center for Climate Change Law at Columbia University.

Exxon's lawyer Theodore Wells claims the $80 proxy represents a global, macro level of costs that was applicable to certain projects but not others. These other projects are called greenhouse gas, or GHG projects, and are calculated using a different set of cost assumptions for different capital projects: "There is no document that says ... proxy costs and GHG costs were one and the same," he said.

A team of researchers at George Mason, Harvard and Bristol universities have been compiling a report that tracks the evidence proving the oil giant has been deceiving investors as well as the American public.

"Climate deniers directly impact the scientific community - and, in turn, its ability to serve the public good - by forcing climate scientists to respond to bad-faith demands and arguably causing a chilling effect pressuring scientists to underplay scientific results," wrote George Mason's John Cook, Harvard's Geoffrey Supran and Australia-based Bristol's Stephan Lewandowsky.