China Post: Australia has overtaken the U.S. as the biggest emitter per person of carbon dioxide, a greenhouse gas blamed for global warming, according to a British risk analysis firm. The average Australian contributes 20.58 tons of CO2 to the atmosphere each year to cool homes, drive cars and generate electricity with coal, the U.K.-based risk assessment company Maplecroft said Thursday. The U.S. fell to second at 19.78 tons per inhabitant a year while Canada was third at 18.81 tons. The …