Reuters: Negotiations seeking a global pact to tackle global warming are troubled and could end in disastrous failure, China’s top climate change envoy warned on Monday, saying rich countries are failing to deliver on promises. China is emerging as the world’s top emitter of the greenhouse gases that stoke dangerous global warming and plays a key role in talks to address the threat. These are supposed to culminate in a new deal in Copenhagen, Denmark, late next year. But Yu Qingtai, …