Ozone layer

The stratosphere contains a layer of relatively high concentrations of ozone from 12 to 40 km above the Earth’s surface, with a peak concentration of about 8 ppm. The ozone layer absorbs most of the UVB light from the sun (UVB is high-energy radiation that causes sunburns).

The ozone layer is depleted each year around Antarctica as a consequence of CFCs and HCFCs released by humans. The use of these substances was phased out under the Montreal Protocol, but they still linger in the atmosphere. They have been replaced by HFCs, which do not deplete the ozone layer but still contribute to global warming.