Exxon Mobil Corp. won a major victory in a closely-watched lawsuit on Dec. 10 when a judge ruled that the company did not defraud investors out of up to $1.6 billion by hiding the true cost of climate change regulation.

The ruling by Justice Barry Ostrager in Manhattan Supreme Court followed a trial featuring testimony from investors, experts and former Exxon Mobil CEO Rex Tillerson.

The judge found that the New York State Attorney General's case failed to produce evidence that investors were misled. It was the first of several climate change lawsuits against major oil companies to go to trial.

Attorney General Letitia James said in a statement that her office "will continue to fight to ensure companies are held responsible for actions that undermine and jeopardize the financial health and safety of Americans." She did not say whether she would appeal.

Exxon Mobil said that the ruling affirmed the company's position that the investigation was "baseless."

"We provided our investors with accurate information on the risks of climate change," spokesman Casey Norton said in a statement.

The state's 2018 lawsuit said Exxon Mobil caused investors to lose up to $1.6 billion by falsely telling them it had properly evaluated the impact of future climate regulations on its business.

It said Exxon Mobil told investors it was projecting the impact of future regulations by using a "proxy cost" of up to $80 per ton of carbon emissions in wealthy countries by 2040, but internally used figures as low as $40 per ton or none at all.

Exxon Mobil countered that the proxy cost and the internal greenhouse gas costs were distinct and used for different purposes.

Ostrager's decision said the evidence supported the company's argument that the two types of projected costs were "different metrics."

"What the evidence at trial revealed is that Exxon Mobil executives and employees were uniformly committed to rigorously discharging their duties in the most comprehensive and meticulous manner possible," the judge wrote.

In October, as the New York trial was getting underway, Massachusetts announced its own lawsuit against Exxon Mobil, including allegations about proxy costs similar to those Ostrager rejected. Unlike New York's lawsuit, Massachusetts accuses Exxon Mobil of misleading consumers, not just investors.

Cities and counties across the U.S. have also sued Exxon Mobil and other oil companies seeking funds to pay for seawalls and other infrastructure to guard against rising sea levels caused by climate change. The companies have denied liability.