



"The acid droplets destroy the stratospheric ozone layer that protects us from harmful solar ultra-violet rays," says Cowley. "They catalyse unreactive forms of man-made chlorine into active free radicals (for example ClO, chlorine monoxide). The radicals destroy many ozone molecules in a series of chain reactions.."

This outbreak of PSCs is truly unusual. "Prior to this outbreak I have seen PSCs over the UK only twice in the last 20 years!" says Cowley. "This episode is exceptional at such low latitudes. If it goes on any longer my camera will be worn out."