False colour image of Antarctic ozone hole, 30 November 1992.

False colour image of Antarctic ozone hole, 30 November 1992. The ozone layer plays a vital role in protecting life on Earth from harmful ultraviolet radiation. Studies begun in the 1970s showed that the ozone layer was thinning. The phenomenon was particularly evident over the poles, where the layer was even disappearing on a seasonal basis. The occurence was linked with the presence in the atmosphere of a group of man-made chemicals which destroy ozone, known as CFCs (chloroflurocarbons), used in refrigerators and aerosols. (Photo by Oxford Science Archive/Print Collector/Getty Images)