UNITED NATIONS -- The Obama administration, in a major environmental policy shift, is leaning toward asking 195 nations that ratified the U.N. ozone treaty to enact mandatory reductions in hydrofluorocarbons, according to U.S. officials and documents obtained by The Associated Press. The Montreal Protocol is widely viewed as one of the most successful environmental treaties because it essentially eliminated the use of chlorofluorocarbons, or CFCs, blamed for damaging the ozone layer over Antarctica. Because they do not affect the ozone layer, HFCs broadly replaced CFCs as coolants in everything from refrigerators, air conditioners and fire extinguishers to aerosol sprays, medical...