World Ozone Day 2027 is on Thursday

About World Ozone Day

The ozone layer is a region of the stratosphere that absorbs much of the Sun's harmful ultraviolet radiation. In the 1970s and 1980s, scientists found that it was being thinned by human-made chemicals such as chlorofluorocarbons (CFCs) and halons, which were used in refrigeration, aerosol sprays, fire extinguishers and other products. World Ozone Day celebrates the international response to that threat.

In 1985 countries adopted the Vienna Convention for the Protection of the Ozone Layer, and on September 16, 1987, they signed the Montreal Protocol on Substances that Deplete the Ozone Layer, which entered into force in 1989 and set schedules for phasing out those chemicals. In 1994 the UN General Assembly proclaimed September 16 the International Day for the Preservation of the Ozone Layer in resolution 49/114. On September 16, 2009, the Vienna Convention and the Montreal Protocol became the first treaties in UN history to achieve universal ratification.

The protocol has kept evolving. In 2016, meeting in Kigali, Rwanda, its parties agreed the Kigali Amendment to phase down hydrofluorocarbons (HFCs), substitute chemicals that spare the ozone layer but are potent greenhouse gases. A UN-backed scientific assessment released in January 2023 found the ozone layer on track to recover to 1980 levels by around 2066 over Antarctica, 2045 over the Arctic and 2040 elsewhere, if current policies stay in place. The 2026 theme was "Global action for a cooler planet," marking ten years since the Kigali Amendment.

Sources: United Nations: International Day for the Preservation of the Ozone Layer, UN News: Ozone layer recovery is on track (January 2023), UN Environment Programme: Ozone Secretariat. How we check dates.

How to mark World Ozone Day

• Wear sunscreen, a hat and sunglasses outdoors, and check the daily UV index where you live.
• Have old refrigerators, freezers and air conditioners collected by a certified recycler so their refrigerants are recovered safely.
• Have home or car air conditioning serviced by a qualified technician to catch refrigerant leaks.
• Explain the ozone layer to kids with a simple lesson on sunlight, UV rays and why sun protection matters.
• Read about how the Montreal Protocol came together as an example of science-led international cooperation.

World Ozone Day dates