Bloomberg: The U.S. shot back today at countries criticizing its opposition to specific targets to cut global warming pollution, saying nations pushing for the reductions are hindering efforts to craft a new climate treaty. The U.S., the only developed nation not to ratify the emissions-limiting Kyoto Protocol, is the main opponent to a United Nations proposal to reduce greenhouse gases by 25 to 40 percent by 2020 from 1990 levels. France and India are among countries condemning the …