Discovered by Schonbein in 1839, ozone (03) is a highly reactive and toxic form of oxygen with a pungent smell. It occurs both naturally and as an atmospheric pollutant at ground level. Ozone is found in low concentrations in the stratospheric layer of the earth's atmosphere, 10 to 50 km above the surface, where it acts to shield the earth from solar UV radiation, between 220 and 320mm (Christie, 2000). Measurements of stratospheric ozone began at Oxford in 1924 where Dobson and Han•ison found seasonal variations in ozone levels. They also found significant variabllity in short term ozone levels, later recognised as being associated with weather patterns and changes in surface air pressure. The units used for measuring ozone concentrations ate known as Dobson units (DU) and represent the amount of ozone in a square centimctle column through the atmosphere. A typical measurement about 300 DU, which means that if you took all the ozone in a vertical column above the instrument down to sea level, it would form a 3mm thick layer. The need for a global network of ozone monitonng stations was soon recognised and with the International Geophysical Year of 1957 - 58 the network expanded to include the first measurements of ozone in Antarctica, from the British Station at Halley Bay on the coast of the Weddell Sea. It was from here that regular ozone monitoring, from the 1960s to the mid 1980s, led to the 1985 report in "Nature"of a 50% spring-time depletion of the ozone layer above Antarctica. In this paper, Farman, Gardiner and Shanklin (1985) linked the reduction in ozone levels to increases in inorganic chlorine and the very low temperatules of the Antarctic stratosphere. The ozone hole had been discovered. Discovered by Schonbein in 1839, ozone (03) is a highly reactive and toxic form of oxygen with a pungent smell. It occurs both naturally and as an atmospheric pollutant at ground level. Ozone is found in low concentrations in the stratospheric layer of the earth's atmosphere, 10 to 50 km above the surface, where it acts to shield the earth from solar UV radiation, between 220 and 320mm (Christie, 2000). Measurements of stratospheric ozone began at Oxford in 1924 where Dobson and Han•ison found seasonal variations in ozone levels. They also found significant variabllity in short term ozone levels, later recognised as being associated with weather patterns and changes in surface air pressure. The units used for measuring ozone concentrations ate known as Dobson units (DU) and represent the amount of ozone in a square centimctle column through the atmosphere. A typical measurement about 300 DU, which means that if you took all the ozone in a vertical column above the instrument down to sea level, it would form a 3mm thick layer. The need for a global network of ozone monitonng stations was soon recognised and with the International Geophysical Year of 1957 - 58 the network expanded to include the first measurements of ozone in Antarctica, from the British Station at Halley Bay on the coast of the Weddell Sea. It was from here that regular ozone monitoring, from the 1960s to the mid 1980s, led to the 1985 report in "Nature"of a 50% spring-time depletion of the ozone layer above Antarctica. In this paper, Farman, Gardiner and Shanklin (1985) linked the reduction in ozone levels to increases in inorganic chlorine and the very low temperatules of the Antarctic stratosphere. The ozone hole had been discovered.