The world is on track to add 700 million new ACs by 2030, and 1.6 billion by 2050, largely in hot, developing countries like India and Indonesia ... Air conditioners use refrigerants, and some of the most common types — hydrofluorocarbons, or HFCs — are powerful greenhouse gases, with thousands of times the warming potential of carbon dioxide. If HFC use continues to grow at its current pace, these chemicals could make up as much as 19 percent of emissions by 2050.