The climate summit in Copenhagen has reached a crucial phase with talks on Thursday set to next 24 hours crucial to determining success or failure, the United Nations climate chief has said. Amid mounting signs of deadlock, Yvo de Boer urged delegates from 193 countries to overcome their differences and produce a deal. "I still believe it's possible to reach a real success," he said on Wednesday. "The next 24 hours are absolutely crucial and need to be used productively.'' On Thursday environment ministers are set to meet for final rounds of negotiations, aiming to salvage a climate pact from...