The US National Oceanic and Atmospheric Administration and NASA said that the ozone hole was the fifth smallest since 1992, the year that the Montreal Protocol, a landmark international agreement to phase out ozone-depleting chemicals began to take effect.The Copernicus Atmosphere Monitoring Service (CAMS) concurred that the 2025 Antarctic ozone hole came to an end on 1 December, marking the earliest closure since 2019. The 2025 ozone hole was also the smallest in five years.