The Montreal Protocol is the only UN treaty ratified by every country on Earth and is successfully healing the ozone layer.

The Montreal Protocol on Substances that Deplete the Ozone Layer was adopted on September 16, 1987, following the discovery of a massive hole in the ozone layer over Antarctica. It targeted chlorofluorocarbons (CFCs) and halons, which were commonly used in refrigerators, air conditioners, and aerosol sprays. When these chemicals reach the stratosphere, solar radiation breaks them down, releasing chlorine and bromine atoms that destroy ozone molecules.As of 2024, the treaty remains the only United Nations agreement to be ratified by all 198 member states. According to a 2022 report by the Scientific Assessment Panel to the Montreal Protocol, nearly 99% of banned ozone-depleting substances have been successfully phased out. This massive reduction has prevented millions of cases of skin cancer and cataracts by limiting harmful ultraviolet (UV) radiation from reaching the Earth's surface.NASA and the National Oceanic and Atmospheric Administration (NOAA) monitor the ozone hole using satellite instruments like the Ozone Mapping and Profiler Suite (OMPS). Their data suggests that if current policies remain in place, the ozone layer will recover to 1980 levels by 2040 for most of the world and by 2066 over Antarctica. The treaty was further strengthened by the 2016 Kigali Amendment, which aims to phase out hydrofluorocarbons (HFCs) to help mitigate global warming.