On October 28, Australia ratified the Kigali Amendment to the Montreal Protocol. Australia is the tenth country to ratify, joining others as diverse as Mali, Norway and Rwanda in a global commitment to dramatically reduce hydrofluorocarbons (HFCs) in the atmosphere. Once 20 countries have ratified the amendment, it will become binding. HFCs were designed specifically to replace ozone-destroying compounds previously used in air conditioners and refrigerants. Unfortunately, we now know that HFCs are massively potent greenhouse gases - thousands of times more powerful than carbon dioxide (albeit released in far smaller quantities).