The ozone layer is a layer of ozone high up in the Earth 's atmosphere stratosphere , between approximately 10 kilometres and 50 kilometres above Earth’s surface. The exact amount of ozone varies, depending on the seasons and the location. ^[1] This layer absorbs between 93 and 99 per cent of the ultraviolet radiation from the s un . ^[2] This radiation is dangerous to living organisms on Earth.

Over the last hundred years, the ozone layer has been damaged by man-made chemicals , especially CFCs ( chlorofluorocarbons ), which were used mainly in aerosol sprays and refrigerants. CFCs are broken down in the upper atmosphere when they react with the ozone, causing ozone depletion . International leaders recognized this and united in banning the use of CFCs. As a result, the hole in the ozone layer has been shrinking and the ozone layer has been recovering. ^[3]

The ozone layer was discovered in 1913 by French physicists Charles Fabry and Henri Buisson . Its properties were explored in detail by the British meteorologist G. M. B. Dobson , who developed a simple spectrophotometer , the Dobsonmeter . This tool could be used to measure the ozone levels found in the stratosphere from the ground. Between 1928 and 1958 Dobson established a worldwide network of ozone monitoring stations. Most of these stations are still in use today. The " Dobson unit ", a convenient measure of the total amount of ozone in a column overhead, is named in his honor.

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