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The United Nations International Day for the Preservation of the Ozone Layer is celebrated each year around the world on September 16, a date that marks the 1987 signing of the Montreal Protocol. This international treaty was enacted to protect the ozone layer by eliminating the use of ozone-depleting substances and has led to the phase-out of 99 per cent of ozone-depleting chemicals in refrigerators, air-conditioners and many other products. These efforts have provided protection for the ozone layer and in doing so, helped to improve human and ecosystem health by limiting incoming harmful UV radiation. 

The focus of World Ozone Day 2025 will center on the theme "From Science to Global Action: 40 Years of the Vienna Convention." This theme commemorates the 40th anniversary of the Vienna Convention for the Protection of the Ozone Layer, highlighting the journey from scientific understanding to global cooperation in protecting the ozone layer.

The theme highlights that the Montreal Protocol, which originated from the Vienna Convention, serves as a model for addressing global environmental challenges, demonstrating the power of global collective action, international cooperation and science-based decision-making.

One of the primary objectives of World Ozone Day is to educate people about the crucial role the ozone layer plays in preserving life on Earth. To this end, primary and secondary school educators throughout the world are encouraged to organize classroom activities that focus on topics related to ozone, the ozone layer and the connection between ozone action and planetary health.

Why Care About The Ozone Layer?

• The ozone layer acts as an atmospheric shield.  All life on earth depends on its protection from the lethal levels of ultraviolet radiation produced by the sun.
• Negative changes in the ozone layer are being offset by positive changes in human behavior, allowing the ozone layer to reform. The role the ozone hole itself plays in global warming and the resulting climate change is small compared to the impacts coming from human activities. (NASA)
• Cause and effect has been established between a thinning of the ozone layer and increased incidence of skin cancer.
• Declines in crop yields of up to 50% in some countries have been linked to increased amounts of incoming UV radiation.  A thinner ozone layer is also a factor in the declining concentrations of phytoplankton that support aquatic food webs.
• Many ozone depleting substances remain active in the atmosphere for 50 to 100 years and most ozone depleting substances are also greenhouse gases.
• Ozone protection efforts to date are making a difference.  Parts of the ozone layer have recovered at a rate of 1-3% per decade since 2000. At projected rates, Northern Hemisphere and mid-latitude ozone will heal completely by the 2030s.  Complete global healing is expected by 2060.
• Actions taken under the Montreal Protocol have safeguarded carbon reserves to the tune of 690 billion metric tons. (estimate as of Aug 2021)
• The effort to preserve the ozone layer shows how collective action guided by science can solve major global crises.