Associated Press: The sharp-tongued U.N. official who shepherded troubled climate talks for nearly four years announced his resignation Thursday, leaving an uncertain path to a new treaty on global warming. Exhausted and frustrated by unrelenting bickering between rich and poor countries, Yvo de Boer said he will step down July 1 to work in business and academia. With no obvious successor in sight, fears were voiced that whoever follows will be far less forceful than the skilled former civil …