McClatchy Newspapers: One question could dominate this week’s gathering of the world’s top economic powers in Italy : Will the United States and Europe act by themselves to cut emissions of the heat-trapping gases that are causing long-term global warming and will they be able to persuade fast-developing nations such as China and India to go along? President Barack Obama will lead a gathering of nations called the Major Economies Forum , looking to forge a consensus for a global pact to stop global warming …