Reuters: World powers have a “very good chance” of reaching a political deal to target global curbs in carbon emissions at a U.N. conference in Copenhagen next month, British climate change expert Nicholas Stern said on Wednesday. Stern, author of an influential 2006 report for the British government on the impact of global warming, said he did not expect a “formal treaty” to be signed in Copenhagen, partly due to resistance in the United States. “But we can and should put together a …