WMO Bulletin was issued for World Ozone Day, celebrated on 16^th September every year, and the 40^th anniversary of the Vienna Convention.

• Ozone layer is expected to recover to 1980 values (before the appearance of the ozone hole) by around 2066 over the Antarctic, by 2045 over the Arctic and by 2040 for the rest of the world.

About Ozone Layer

• Ozone layer sits in the stratosphere between 15 km and 30 km above the earth and shields us from the Sun’s harmful ultraviolet radiations. 
• Ozone Depleting Substances (ODS): ODS release chlorine or bromine which destroy ozone molecules. 
  • ODS that release chlorine include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon tetrachloride (CTC), and methyl chloroform while that release bromine include halons and methyl bromide. 
• Depletion of stratospheric ozone is more pronounced in the Southern Hemisphere (Antarctica) than in Northern Hemisphere (Arctic). 

Vienna Convention 1985

• It was the first global treaty recognizing stratospheric ozone depletion as a problem and established the framework for international cooperation on ozone. 
• It paved the way for Montreal Protocol on Substances that Deplete the Ozone Layer, adopted in 1987. 
  • Montreal Protocol has led to the phase-out of over 99% of the production and consumption of controlled ODS. 
• Kigali Amendment to Montreal Protocol was adopted in 2016 for phase-down of hydrofluorocarbons (HFCs), a greenhouse gas used as a substitute for ODS.