Greenwire: Is Big Oil warming at last to the notion of an alternative-energy future? So say some analysts who are pondering Exxon Mobil Corp.’s recent moves. Breaking from years of steadfast commitment to fossil fuels, the behemoth has announced big investments in electric cars, unconventional natural gas and algae-based biofuels (Greenwire, July 14). "I think they see changes to the energy system coming over the next decades," said Michael Webber, an energy expert and engineering …