Associated Press: The Obama administration called hydrofluorocarbons widely used in refrigerators and air conditioners “a very significant” threat to climate change Monday, and expressed a preference for drastically reducing HFCs that are promoted under the U.N.’s ozone treaty rather than phasing them out entirely. But a senior State Department official stopped short of endorsing a formal proposal last week by the two small island nations of Micronesia and Mauritius to alter the ozone treaty known as …