Who’s Al Gore’s latest environmental ally? How about Rex Tillerson, CEO of Exxon Mobil. Something must be afoot. In a speech in Washington, Tillerson said he favored a flat carbon tax imposed on greenhouse-gas emissions, rather than the politically more-viable cap-and-trade system. Tillerson called a flat tax a "more direct, a more transparent, and a more effective approach." A fellow at the Center for American Progress thinks, however, that Tillerson is bluffing. Calling for a carbon tax could be a ploy because few observers believe such a tax is politically feasible in our Congress," said Daniel J. Weiss.