Canadian Press: A showdown between the world’s two largest polluters loomed over the United Nations climate talks Tuesday as China accused the United States and other rich countries of backsliding on their commitments to fight global warming. Trying to ease the tension, UN Secretary General Ban Ki-moon said rich and poor countries must “stop pointing fingers” and should increase their pledges to cut greenhouse gas emissions to salvage the faltering talks on a climate pact. The 27-member …