. . . "o pledges after they expire at the end of 2012.But it will do so, it says, only if major emitters - including the US and emerging giants such as China - back plans for a new binding pact that would be completed by 2015 and take effect by 2020, when the current roster of voluntary pledges runs out.This would achieve what the nearly disastrous Copenhagen Summit of 2009 failed to do: Forge a worldwid" . .