"When we think of the gases that contribute to climate change, carbon dioxide comes to mind first -- with good reason. CO2 accounts for about 82 percent of greenhouse gas emissions in the United States, and persists for centuries.
But other gases contribute to climate change as well, some of which are many times more potent than CO2 though less abundant in the atmosphere. One class of these is hydrofluorocarbons, or HFCs, gases used in many air conditioners and refrigerators. HFCs can be up to 10,000 times more damaging to the climate than CO2 -- and absent ambitious action to limit their use, HFC emissions are projected to triple in the U.S. by 2030...."