Negotiators grab head start on monumental climate challenge

By Barbara Lewis and Bate Felix PARIS (Reuters) - Senior negotiators from almost 200 nations on Sunday began thrashing out a new global deal to curb climate change as the president of China, the world's biggest polluter, landed in Paris. The United Nations conference begins at summit level on Monday, when more than 150 heads of state and government - including U.S. President Barack Obama and Chinese President Xi Jinping - will attend talks at a sprawling complex north of the French capital. Fren