http://www.nytimes.com/2012/02/16/science/earth/us-pushes-to-cut-emissions-that-speed-climate-change.html?_r=1&scp=1&sq=U.S.%20Pushes%20to%20Cut%20Emissions%20of%20Some%20Pollutants%20That%20Hasten%20Climate%20Change&st=cse