Reuters: A top U.N. official suggested a 2020 greenhouse gas goal for developing nations on Thursday as part of a new U.N. climate pact as China and the United States sought common ground to fight global warming. Many nations expressed worries about a lack of urgency in the negotiations, less than two months before 190 nations are meant to agree a new U.N. pact in Copenhagen to succeed the existing Kyoto Protocol. In New Delhi, Yvo de Boer, head of the U.N. Climate Change Secretariat, …