Summary Companies US points to $400 billion in climate subsidies US unveils rules to cut own methane output Major fossil firms pledge to cut emissions from own operations 56 countries commit to accelerating decarbonisation of industry DUBAI, Dec 2 (Reuters) – U.S. Vice President Kamala Harris sought to claim the mantle of global climate leadership for the United States on Saturday in a speech to the COP28 summit, listing a slew of initiatives to cut emissions and harness renewable energy in the world's largest oil and gas producer. The address came on the second day of back-to-back speeches by world…