Associated Press: The U.N. climate chief said Thursday he is encouraged by the climate views of the three contenders in the U.S. presidential election. Republican John McCain and Democrats Barack Obama and Hillary Rodham Clinton have all expressed support for some form of mandatory controls on carbon emissions, usually involving a "cap-and-trade” system that allows polluters to buy and sell allowances. "I’m really encouraged to see that all three of the presidential front-runners …