"We stopped funding them in the middle part of the past decade because a handful of them were making the uncertainty of the science their focal point," Cohen said. "Frankly, we made the call that we needed to back away from supporting the groups that were undercutting the actual risk" of climate change. "We recognize the risk," Cohen added. He noted that Exxon Mobil, after an acquisition in 2009, had become the largest producer of natural gas in the United States. Because natural gas creates far less carbon dioxide than coal when burned for electricity, the company expects to be a prime beneficiary of President Obama's plan to limit emissions. Exxon Mobil has also endorsed a tax on emissions as a way to further reduce climate risks.