Reuters: In a strategic shift, theUnited Nations has stopped urging nations to commit to tougherpledges to curb carbon emissions, fearing further debate couldderail already fraught talks on a more ambitious climate pact. It is better to start with pledges already offered andbuild from there, officials say, given the short time left tohammer out a pact that broadens the existing Kyoto Protocol bysigning up all major emitters to fight climate change. This effort is critical to ensure …