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On 16 September, the world will mark the International Day for the Preservation of the Ozone Layer. It was on this day, 35 years ago, that the , considered one of the most significant environmental agreements for humanity, was adopted. 

Let¡¯s look at how this agreement was critical in protecting the health of our planet and all its species, while also reducing greenhouse gases in the atmosphere. 
 

What is the ozone layer?

The ozone layer is a thin shield of gas in the Earth¡¯s atmosphere that protects the planet, absorbing the sun¡¯s ultraviolet (UV) rays and helping to preserve all life on the planet. But the ozone layer is not immune to harmful human activities. A collection of human-made greenhouse gases known as ozone-depleting substances (ODSs), including chlorofluorocarbons that can be found in everyday products such as air conditioners, refrigerators, and aerosol cans, have been destroying the ozone layer. 

Why does it matter?

The consequences of any damage to the ozone layer are multifold. Harmful ODSs can carve a hole in the ozone layer, allowing UV rays to directly hit the Earth. Long-term exposure to UV radiation threatens human life - causing skin cancer, eye diseases and other health problems - and seriously harms most animals, plants, and microbes. Moreover, many ozone-depleting substances are also potent greenhouse gases that contribute to climate change when they accumulate in the atmosphere and warm the planet.  

A crisis averted - the Montreal Protocol and the Kigali Amendment

¡°We celebrate 35 years of the Montreal Protocol¡¯s success in protecting the stratospheric ozone layer against synthetic chemicals that also cause climate heating,¡± in his message to mark the international day. 

The Montreal Protocol, which was adopted in 1987 and entered into force in 1989, is considered one of the world¡¯s most successful environmental treaties. ¡°Thanks to a global agreement, humanity has averted a major health catastrophe due to ultraviolet radiation pouring through a massive hole in the ozone layer,¡± the Secretary-General said.

The Protocol provides a set of practical ways to phase out ODSs ¨C including through stringent measures worldwide to control products containing the chemicals.

In 2016, the Protocol was amended in Kigali to also phase out the production and use of hydrofluorocarbons (HFCs) - which became a replacement for ODSs but proved to be more potent than carbon dioxide, and detrimental to the climate. 

According to the UN Environment Programme (UNEP), thanks to the agreement, there has been a substantial reduction in ODSs emissions over the last two decades, and there is evidence that the ozone layer is healing itself and can recover by the middle of this century. is expected to close by the 2060s, while other regions will return to pre-1980s values even earlier. To date, of ODSs have been phased out.