If you remember the lesson about Montreal gases, you remember that halocarbons are man-made compounds which act as greenhouse gases. The gases which were phased out contributed to the depletion of the ozone layer (the ones which contained chlorine). However, in A/Cs and refrigerators, they were replaced by other types of halocarbon – the one which does not contribute to the ozone layer depletion but still acts as a greenhouse gas.
Most of the aircons use HFC (hydrofluorocarbon), a halocarbon and greenhouse gas that has much stronger heat-trapping power than CO2. The leaks of this compound happen most of the time during the production or disposal. But driving the demand for aircons, we also drive emissions of halocarbons. In 2019, an amendment to the Montreal Protocol included HFC as a gas to phase out. After ratifications, the countries producing A/Cs with this coolant will need to look for new solutions.