How the Ozone Layer Works

In September 2026 the Copernicus Atmosphere Monitoring Service reported that the Antarctic ozone hole grew faster than usual, reaching about 25 million square kilometres on 12 September, although other measures stayed close to average. This film explains what sits behind that number: what ozone is and where the ozone layer lies; how little of it there is, measured in Dobson units; how it blocks the Sun's harmful ultraviolet light; how sunlight makes and breaks ozone in the Chapman cycle; how chlorofluorocarbons carry chlorine into the stratosphere, where one chlorine atom can destroy tens of thousands of ozone molecules; how British scientists found the hole over Antarctica in 1985; why it forms there, in the polar vortex and its icy clouds; and how the Montreal Protocol of 1987 cut the chemicals so that the layer is expected to recover by about 2066.

How the ozone layer works

A thin shield, a hole, and a repair.

The thin shield

Made by sunlight, torn by chlorine, mended by a treaty.

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