Ozone depletion

Story hook

In 1985, three British scientists at a remote Antarctic station published a finding so alarming that NASA initially thought its own satellites were malfunctioning: a vast "hole" in the ozone layer had opened over the South Pole. The thinning was so severe that protective software had been automatically discarding the readings as errors. The culprit turned out to be a class of "miracle" chemicals — chlorofluorocarbons (CFCs) — used in refrigerators, air conditioners, aerosol sprays and foams. Once released, they drifted up to the stratosphere where ultraviolet light split them apart, unleashing chlorine atoms that destroyed ozone molecules by the thousands.

The world's response became the greatest environmental success story in history. In just two years, nations signed the Montreal Protocol (1987) — the only UN treaty ever ratified by every single country on Earth — and began phasing out CFCs. It worked. The ozone layer is now healing, on track to recover by the middle of this century.

But there was a twist. The chemicals that replaced CFCs — HFCs (hydrofluorocarbons) — were kind to the ozone layer but turned out to be super-potent greenhouse gases, thousands of times worse than CO₂ for global warming. So in 2016, the Montreal Protocol evolved again, with the Kigali Amendment, to phase these down too. The story of the ozone layer is the rare case where the world saw a planetary threat, acted decisively — and won.

Why this matters for UPSC

A reliable Prelims scorer and a favourite Mains/interview example of successful international environmental cooperation. Prelims tests the Vienna Convention vs Montreal Protocol, the ODS (CFCs/halons), the Kigali Amendment (HFCs), the ozone hole, and Dobson Units. Mains and interviews use Montreal as the "how to make a climate treaty work" template (contrast with the slower UNFCCC). It links pollution, the atmosphere and climate policy.