September 16 marks the 40th anniversary of the Vienna Convention for the Protection of the Ozone Layer and the upcoming 2025 International Day for the Preservation of the Ozone Layer. On this day, the World Meteorological Organization (WMO) released the “WMO Ozone Bulletin,” pointing out that ozone depletion observed in 2024 remains at low levels, Earth’s protective ozone layer is recovering, and is expected to continue doing so over the coming decades.
The bulletin notes that in 2024, the depth of the Antarctic ozone hole is below the 1990–2020 average level, and its area is also smaller than the levels observed between 2020 and 2023. Part of the reason is year-to-year fluctuations caused by naturally occurring atmospheric factors. However, the long-term positive trend reflects the success of united international action.
The Vienna Convention for the Protection of the Ozone Layer acknowledges that the depletion of stratospheric ozone is a global issue and provides a framework for mobilizing international cooperation in ozone research, systematic observation, and scientific assessment.
In his message for the International Day for the Preservation of the Ozone Layer, UN Secretary-General António Guterres stated that 40 years ago, guided by science and united action, countries took the first step to protect the ozone layer. The Vienna Convention and its Montreal Protocol on Substances that Deplete the Ozone Layer have become milestones in successful multilateral action. Today, the ozone layer is healing. This achievement shows that progress in protecting the ozone layer is possible when countries heed scientific warnings.
The bulletin points out that, to date, the Montreal Protocol has eliminated more than 99% of the production and consumption of ozone-depleting substances under restriction, which were used in air conditioning, fire-fighting foam, hair spray, and other applications. As a result, the ozone layer is expected to recover to its 1980s levels by the middle of this century, significantly reducing the risk of skin cancer, cataracts, and ecosystem damage caused by excessive ultraviolet radiation.
WMO Secretary-General Petteri Taalas stated that this year’s theme for the International Day for the Preservation of the Ozone Layer is “From Science to Global Action,” echoing the slogan for WMO’s 75th anniversary, “Science for Action.” WMO’s scientific research on the ozone layer dates back decades and is built upon trust, international cooperation, and a commitment to free data exchange—these are the cornerstones for achieving the world’s most successful environmental agreements.