JOHANNESBURG (AP) -- Experts say cutting hydrofluorocarbons, or HFCs, is the fastest way to reduce global warming. The United States, the worldamp;apos;s second-worst polluter, is among the countries that want to quickly phase out the use of HFCs, and now it is bound to take the earliest action, starting by 2019. Hereamp;apos;s a look at what it all means....