WMO Reports Healing Ozone Layer as 2024 Antarctic Hole Shrinks, Marking Global Progress

The Earth’s protective ozone layer is showing clear signs of recovery, with the ozone hole in 2024 measuring smaller than in recent years, according to the latest World Meteorological Organization (WMO) Ozone Bulletin. Released on World Ozone Day, 16 September 2025, the report marks the 40th anniversary of the Vienna Convention, the international treaty that first galvanized global cooperation to address ozone depletion.

A Positive Trend After Decades of Global Action

The WMO noted that the relatively low level of ozone depletion in 2024 was partly due to natural atmospheric variability, but stressed that the long-term recovery is a direct result of global action under the Montreal Protocol and subsequent agreements.

UN Secretary-General António Guterres highlighted the milestone: “Forty years ago, nations came together to take the first step in protecting the ozone layer—guided by science, united in action. The Vienna Convention and its Montreal Protocol became a landmark of multilateral success. Today, the ozone layer is healing. This achievement reminds us that when nations heed the warnings of science, progress is possible.”

Since the adoption of the Montreal Protocol in 1987, over 99% of ozone-depleting substances (ODS) have been phased out worldwide. These chemicals, once widely used in refrigeration, air conditioning, firefighting foams, and even aerosol sprays, were identified as the primary culprits in destroying stratospheric ozone. Thanks to the treaty’s enforcement, the ozone layer is projected to return to 1980 levels by mid-century, greatly reducing risks of skin cancer, cataracts, and ecosystem damage caused by excessive UV radiation.

2024 Ozone Hole: Signs of Recovery

The Antarctic ozone hole, which appears each spring, was smaller in 2024 compared to the 2020–2023 period. The WMO reported:

• A maximum ozone mass deficit (OMD) of 46.1 million tonnes on 29 September 2024.

• This value was below the 1990–2020 average, indicating a positive deviation.

• The onset of depletion was later than usual, with recovery occurring relatively quickly after the peak deficit.

Scientists identified this delayed onset as a strong indicator of initial recovery, suggesting that efforts under international agreements are beginning to yield measurable atmospheric improvements.

The Role of Monitoring and Science

WMO Secretary-General Celeste Saulo emphasized the critical role of scientific collaboration: “The theme for World Ozone Day is From Science to Global Action. It mirrors WMO’s 75th anniversary slogan Science for Action. This is no coincidence. WMO’s decades of research on the ozone layer, underpinned by trust, collaboration, and free data exchange, have been key to the success of the Montreal Protocol.”

WMO’s Global Atmosphere Watch Programme has been central in supporting international agreements, providing systematic observations, calibration standards, and intercomparison campaigns to ensure reliable and policy-relevant ozone and UV data.

The Montreal Protocol, Kigali Amendment, and Climate Links

The 2016 Kigali Amendment to the Montreal Protocol expanded the scope of action to include hydrofluorocarbons (HFCs)—potent greenhouse gases that replaced ODS but contribute significantly to global warming. To date, 164 countries have ratified the Amendment, and its phase-down is expected to prevent up to 0.5°C of global warming by 2100.

The success of these agreements demonstrates how environmental policy can deliver dual benefits—protecting the ozone layer while mitigating climate change.

Scientific Assessments and Future Outlook

The UN Environment Programme (UNEP) and WMO co-sponsor a quadrennial Scientific Assessment of Ozone Depletion. According to the most recent 2022 assessment, if current policies remain in place:

• The ozone layer will recover to 1980 levels by 2066 over Antarctica.

• Recovery is expected by 2045 over the Arctic.

• The rest of the world could see full recovery by 2040. The next assessment will be released in 2026, providing updated projections and policy recommendations.

Broader Impacts and Sustainable Development

Protecting the ozone layer directly supports multiple UN Sustainable Development Goals (SDGs):

• SDG 3 (Good Health and Well-Being): Reduced UV exposure lowers risks of skin cancer and eye disease.

• SDG 13 (Climate Action): Synergies with greenhouse gas reductions strengthen climate resilience.

• SDG 2 (Zero Hunger) & SDG 15 (Life on Land): Healthier ecosystems protect crops, biodiversity, and food security.

Matt Tully, Chair of the WMO Scientific Advisory Group on Ozone and Solar UV Radiation, cautioned that the work is not complete: “Despite the success of the Montreal Protocol, continued systematic monitoring of both ozone and ozone-depleting substances is essential. We must ensure that replacements for ODS are safe for both the ozone layer and the climate.”

A Model for Multilateral Success

The story of the ozone layer is now widely regarded as one of the most successful environmental achievements in history, showing that science-based policymaking, global cooperation, and long-term commitment can reverse even the most alarming planetary crises.

As the world grapples with climate change, the ozone success story serves as a reminder that collective action, when grounded in science and solidarity, can deliver transformative results for people and the planet.