Reuters: The fight over climate change has spread to the U.S. Chamber of Commerce, where prominent members of the American big-business lobby — including Nike, Johnson & Johnson and Exelon — are publicly disputing the group’s stance on global warming legislation. The most recent critic, Exelon Corp, announced on Monday it would not renew its membership in the chamber. The decision by the largest nuclear operator in the United States followed moves by California utility PG&E Corp and …