EPA Chief Gina McCarthy wants the world to stop using hydrofluorocarbons (HFCs) in air conditioners and other consumers products as part of President Barack Obama's plan to fight global warming. McCarthy is so determined to make this happen, she's taking the lead role at an ongoing United Nations summit to expand the current global treaty covering ozone-depleting substances. The EPA chief hopes that her agency's recent HFC regulations will convince other countries to join the U.S. in limiting the chemicals. "Because of the importance of taking aggressive action on these chemicals to achieve global climate goals, I will be leading...