Ozone (O3) is a pale blue gas, slightly soluble in water is constantly being produced and destroyed by various reactions associated with ultraviolet light from the sun. Normally, the production and destruction balances, so the amount of ozone at any given time is pretty stable. Ozone helps shield us from damaging or harmful ultraviolet rays.
Over the years it has been reported that human activity has changed the natural balance. For example, manufactured substances such as chlorofluorocarbons and hydrochlorofluorocarbons have been known to destroy stratospheric ozone much faster than it is formed.
The Montreal Protocol on substances that deplete the ozone layer, an international treaty designed to protect the ozone layer by phasing out the production of numerous substances was opened for signature in September 1987, and entered into force on January 1, 1989.
And even though the production of chlorofluorocarbons has stopped for some fifteen years, a paper in the British science journal, Nature reports that an ozone hole five times the size of California has opened over the Arctic for the first time. The loss of ozone is largely put down to a deep cold, which causes water vapor and molecules of nitric acid to condense into clouds in the lower stratosphere.
The graphic is a NASA image showing ozone at about 20km altitude. Red represents large ozone, purple and grey represent very small ozone amounts, and the white line marks the area within which chemical ozone destruction takes place. Source: The Australian and AFP
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