New York (CNN)A trial in which energy giant ExxonMobil stands accused of misleading investors about the potential impact of climate change regulations on its operations started Tuesday.
The New York attorney general brought the suit alleging the company used figures internally that were different from what they disclosed publicly when calculating the impact of laws, taxes and other economic aspects of climate change over the coming decades.
The fraud cost investors as much $1.6 billion, the attorney general's office alleges.
Former US Secretary of State Rex Tillerson was the CEO of ExxonMobil from 2006 to 2016, during the years in question, and will testify in the trial, according to a company attorney.
"Investors cared about these costs because increasing carbon and greenhouse gas regulations had the potential to hurt the profitability and even threatened the viability of Exxon's carbon intensive business," Kevin Wallace, an attorney representing the New York attorney general, told the court.
ExxonMobil calculated an all-encompassing dollar figure for all climate change regulations that would impact demand, such as automobile fuel economy rules or windmill subsidies that would decrease the need for oil, the company's attorney Theodore Wells said.
It gave another dollar amount to "greenhouse gas costs," which were direct charges to specific operational investments, such as fees assessed for smokestacks at a refinery.
The company forecast that by 2040 the demand side would have a financial impact from climate change regulation of $80 per ton, but only $40 per ton on the operational side, and in some cases it used alternative methodologies of calculating costs.
But the New York attorney general says only the larger figure was made public.
"Exxon was only using those higher costs in assessing oil and gas demand. Exxon was not using its publicly disclosed costs when evaluating investments," Wallace told the court. "If the cost from climate change regulation increased the way Exxon told its investors it expected it would, some of Exxon's assets would have been significantly less profitable."
For example, an oil field might not be worth developing if demand dropped or the cost of regulations increased, and that could make the company less valuable to investors.
ExxonMobil disputes the allegations and says the different numbers represented different aspects of the impact of climate change, which will have different financial implications.
"For many years, ExxonMobil has acknowledged that climate change is real and is a problem that must be addressed by the nations of the world," Wells, the ExxonMobil attorney, told the court. "But the problem with climate change does not permit the New York attorney general to bring a meritless complaint."
When Tillerson became ExxonMobil CEO in 2006, he identified that climate change regulation would have a major impact on the company's business and created the process of assessing a dollar amount for it..
"I had taken the view and we had taken the view as a corporation that the risk of climate change was serious and that ... appropriate action was to be needed," Tillerson said, according to the transcript of his deposition.
Wells noted specific disclosures that included caveats such as saying the company would apply the figures "where appropriate," and argued that cashflow projections for unidentified investment projects could not be material for this kind of case.
Wells suggested this case was not brought because of what ExxonMobil had done, but was rather the result of climate change activists opposed to fossil fuel companies trying to falsely vilify ExxonMobil.
A group of activists held a demonstration outside the courthouse before the trial started.
"We think it highlights the deception that Exxon has put forth over the last 50-plus years. You know, my entire life Exxon has been sowing doubt and disinformation about the climate crisis," Lindsay Meiman, a spokeswoman with the group 350.org, which opposes the use of fossil fuels, told CNN.
"We're escalating the demand that is rising around the world for fossil fuel companies to pay for their destruction and what they knew and lied about climate change," she said.