A Beijing man wears a mask in heavy smog last month. The pollution is one… ENLARGE A Beijing man wears a mask in heavy smog last month. The pollution is one reason China recently unveiled long-range plans to curb emissions. Getty Images The U.S., Europe and China are about to confront the gulf between their carbon-cutting ambitions and those of less industrialized countries. President Barack Obama and Chinese President Xi Jinping surprised many observers last month by jointly unveiling long-range plans to curb carbon-dioxide emissions. The move followed a pledge by the other big carbon-emitting economy, the European Union, to reduce greenhouse gases as part of a new round of United Nations-led climate negotiations. Those talks have begun this week in Lima, Peru, and will continue on a higher level next week. But officials and experts say there is little evidence most other developing economies will follow China’s lead. […]