Economist: IN THEORY, the world’s governments have over seven months to craft a new treaty to slow climate change before a deadline set by the United Nations. But in practice, points out Yvo de Boer, head of the UN agency that monitors the current Kyoto protocol, only a few weeks of scheduled negotiations remain. Yet with America’s tree-hugging new leadership in place, and with a green stimulus suddenly in vogue, the outlook for a deal at the climate jamboree in Copenhagen at the end of the year …