Oil major Exxon Mobil Corp. is engaging in industry talks on possible U.S. greenhouse gas emissions regulations and has stopped funding groups skeptical of global warming claims — moves that some say could indicate a change in stance from the long-time foe of limits on heat-trapping gases... [A spokesman] said Exxon in 2006 stopped funding the Competitive Enterprise Institute, a nonprofit advocating limited government regulation, and other groups that have downplayed the risks of greenhouse emissions. [also refers to BP, Shell]