'I call for[…] greater leadership as we strive to implement the Paris Agreement on climate change and mobilize the ambitious climate action we so urgently need at this time,' said the United Nations Secretary-General Antonio Guterres in his message on the International Day for the Preservation of the Ozone Layer (16 September).

The US President Donald Trump has announced that Washington would withdraw from the deal that was signed by 200 countries during course of years.

'When science showed us that chlorofluorocarbons (CFCs) and other substances were tearing a hole in the ozone layer that protects all life on earth, the world responded with determination and foresight by banning them. Thanks to this global commitment, the ozone layer is expected to return to its 1980 levels by mid-century,' he said, according to the UN Information Center (UNIC) in Tehran.

Referring to the landmark Kigali Amendment, which enters into force on 1 January 2019, on hydrofluorocarbons (HFCs) used in cooling systems, the UN Chief said, 'So far, 46 countries have ratified this new instrument; I call on all others to follow suit and show their commitment to a healthier planet. I expect countries to demonstrate significant progress in implementing the Kigali Amendment at the Climate Summit I am convening in September 2019.'

For over three decades, the Montreal Protocol has done much more than shrink the ozone hole; it has shown us how environmental governance can respond to science, and how countries can come together to address a shared vulnerability.