Context:

• The ozone layer which protects life on Earth from high-energy radiation is actually thinning out in the lower stratosphere, new research has found.
• In the 20th century, when excessive quantities of ozone-depleting chlorinated and brominated hydrocarbons were released into the atmosphere, the ozone layer in the stratosphere thinned out globally.
• The Montreal Protocol introduced a ban on these long – lasting substances in 1989.
• New study showed that despite the ban on chlorofluorocarbons (CFCs), the concentration of ozone in the lower part of the stratosphere (15 to 24 km) (where the ozone layer is at its densest) has continued to decline.

About Montreal Protocol:

• The Montreal Protocol (a protocol to the Vienna Convention for the Protection of the Ozone Layer) is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion.
• It was signed in 1987.
• The principal aim of Montreal Protocol is to protect the ozone layer by taking measures to control total consumption of these chemicals.

About Kigali Amendment:

• It amends the 1987 Montreal Protocol.
• Its aims to reduce Hydrofluorocarbons (HFCs) by roughly 80-85 Percent by the late 2045.
• It will be binding on member countries from 2019.

Decreasing order of concentration of greenhouse gases in earth atmosphere

Water vapor (H2O) > Carbon dioxide (CO2) > Methane (CH4) > Nitrous oxide (N2O) > Ozone (O3) > Chlorofluorocarbons (CFCs) > Hydrofluorocarbons (incl. HCFCs and HFCs)

Decreasing order of the gases on the basis of Global Warming Potential

Sulfur hexafluoride (SF6)> Hexafluoroethane (C2F6) >Tetrafluoromethane (CF4) > HCFC-22 (CHClF2) >CFC-12 (CCl2F) >Nitrous oxide (N2O) > Methane (CH4) > Carbon dioxide (CO2)

Source:TH & Wiki