Also: ozone hole, Montreal Protocol, Kigali Amendment
Definition
The thinning of the ozone layer in the stratosphere, mainly caused by man-made chlorine and bromine compounds such as CFCs and halons, which allows more harmful ultraviolet-B radiation to reach the Earth's surface.
Ozone is a molecule of three oxygen atoms. Close to the ground it is a harmful pollutant, but high in the stratosphere it forms a thin shield that absorbs most of the sun's ultraviolet-B rays, which damage DNA, cause skin cancer and cataracts, and harm plants and plankton. In 1974 the chemists Mario Molina and Sherwood Rowland warned that chlorofluorocarbons (CFCs), then widely used in refrigerators, aerosol sprays and foams, could rise to the stratosphere and destroy ozone. In 1985 scientists of the British Antarctic Survey reported a dramatic seasonal fall in ozone over Antarctica, the so-called "ozone hole".
The international response was unusually fast. The Vienna Convention for the Protection of the Ozone Layer (1985) set a framework, and the Montreal Protocol (1987) set binding phase-out schedules. Over time, amendments added more chemicals and sped up timelines. The Montreal Protocol became the first UN treaty to achieve universal ratification.
Create a free account to read 5 full pages a month, or upgrade for unlimited access. The definition above, the A–Z index and the pop-up definitions in lessons stay free.
