Updated

Nations are striving for a deal to start phasing out hydrofluorocarbons from air conditioners and refrigerators to help fight climate change.

They could seal an agreement Friday.

At issue are greenhouse gases far more powerful than carbon dioxide. HFCs, as they're known, were introduced in the 1980s as an answer to ozone-depleting gases. But their danger has grown as air conditioner and refrigerator sales have soared in emerging economies like China and India.

Scientists say eliminating HFCs could put a half-degree Celsius dent in global warming by the end of the century.

Major economies are still debating how fast to phase out HFCs. The U.S. and Western countries want quick action. Nations such as India don't want to face reductions until after 2030, perhaps.