Science determined that there was a hole in the ozone layer by measuring concentrations of ozone at altitude, and finding that the concentration in the Antarctic was very low compared to that elsewhere in the world.

British scientists began their measurements of Antarctic ozone in 1957. The aim was to understand the important role that ozone plays through absorbing solar energy, in determining the temperature profile of the stratosphere and its wind circulation.

The discovery by the British Antarctic Survey (BAS) of the Antarctic ozone hole provided an early warning of the dangerous thinning of the ozone layer worldwide, and spurred international efforts to curb the production of CFCs. The amount of ozone overhead should follow a regular seasonal pattern.

The Antarctic ozone layer did so for the first 20 years of BAS measurements, thereafter clear deviations were observed. In every successive spring the ozone layer was weaker than before, and by 1984 it was clear that the Antarctic stratosphere was changing progressively. This phenomenon is the result of emissions, mainly in the northern hemisphere, of chlorofluorocarbons (CFCs) and halons. These gases are in widespread use in refrigeration, industrial solvents and fire control.

Ozone is destroyed in the Antarctic spring by chlorine formed during the sunless winter. The chlorine is generated by an unusual reaction between stable molecules, on the surface of small stratospheric cloud particles which can only form in the intense cold of the polar winter. The stable molecules obtain their chlorine from CFCs which have previously been broken up in sunlit regions. (Taken from the The British Antarctic Survey Homepage).

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