Antarctic ozone hole. Coloured satellite image of the reduced atmospheric ozone layer over Antarctica on 13th September 2007. Ozone layer thicknesses are colour coded from purple (lowest) through blue, cyan, green and yellow to orange (highest). The purple regions have an ozone layer that is about 40% thinner (at 100-200 Dobson units) than normal (300-340 Dobson units). Ozone absorbs harmful ultraviolet (UV) radiation from the Sun, but its levels are reduced by chlorofluorocarbons (CFCs) and other compounds. The hole in September 2006 (see E100/264) set records for extent (over 29.5 million square kilometres) and ozone depletion (to 85 Dobson units). Here, the hole is smaller, spanning 24.7 million square kilometres. Data from the Ozone Monitoring Instrument on the Aura satellite.