Why this matters now
The ozone story is a prelims favourite — the layer’s role, CFCs and the ozone hole, and the Montreal Protocol/Kigali Amendment (which also helps climate) are repeatedly tested.
The ozone layer
The ozone layer (in the stratosphere) absorbs most of the Sun’s harmful ultraviolet (UV-B) radiation, protecting life from skin cancer, cataracts and ecological damage. (Note: ozone at the surface is a pollutant — “good up high, bad nearby”.)
Causes and the ozone hole
Ozone is destroyed by Ozone-Depleting Substances (ODS) — chiefly chlorofluorocarbons (CFCs), halons and others (from refrigerants, aerosols, foams). The chlorine they release catalytically destroys ozone, most dramatically forming the Antarctic ozone hole each spring.
The Montreal Protocol
The Vienna Convention (1985) and the Montreal Protocol (1987) phased out ODS — a rare, near-universal success; the ozone layer is now healing. The Kigali Amendment (2016) added a phase-down of hydrofluorocarbons (HFCs) — which, though not ozone-depleting, are potent greenhouse gases — giving a major climate co-benefit. India has ratified Kigali.
UPSC angle
Know the stratospheric ozone’s UV role (good up high/bad nearby), CFCs/ODS and the ozone hole, the Vienna Convention/Montreal Protocol, and the Kigali Amendment (HFC phase-down, climate co-benefit).
Frequently asked questions
Why is the ozone layer important?
It absorbs most of the Sun’s harmful UV-B radiation, protecting life from skin cancer, cataracts and ecological damage.
What causes ozone depletion?
Ozone-depleting substances, chiefly chlorofluorocarbons (CFCs), which release chlorine that destroys ozone.
What is the Montreal Protocol?
A 1987 treaty that successfully phased out ozone-depleting substances, allowing the ozone layer to heal.
What is the Kigali Amendment?
A 2016 amendment to the Montreal Protocol that phases down HFCs — potent greenhouse gases — giving a climate co-benefit.