It was early in 1985 that the scare started. It began on the pages of the prestigious science journal Nature, in a now-famous paper by Antarctic expert Joe Farman and two colleagues. The paper announced the presence of the "Ozone Hole".
As is now well known, ozone is a chemical variant of oxygen, having three atoms instead of the usual two. There is only a tiny amount of it in the atmosphere, so little that if it were all brought down to the surface of the Earth and laid like a carpet at our feet at normal atmospheric pressure it would form a layer only 3 mm thick.
As it is, the ozone is dispersed throughout the entire atmosphere, although nearly 90 per cent of it is to be found in a relatively thin layer starting about 13 miles above the ground.
Despite its sparsity, ozone has the useful property of acting as a filter to screen us from the sun's harmful ultraviolet radiation, overexposure to which can cause skin cancer, eye cataracts and other ailments. UV radiation also affects crop yields and aquatic life.
The ozone hole that Farman and his friends discovered is the evocative name applied to the dramatic decrease in ozone concentrations that has been found to occur every spring high over the South Pole. Each year the decrease becomes obvious in September, just as the sun begins to peep over the horizon after the long polar night.
It continues into October when it reaches a minimum, up to 50 per cent below normal values, and then in late October or November the "hole" fills up again, and ozone concentrations return to near their normal values. Although the Antarctic region is relatively unpopulated, the dangers associated with a weakening of the ozone layer come closer to home when the ozone-depleted air drifts into the lower latitudes of the southern hemisphere later in the year.
And so it is that at this time every year many meteorologists fix their gaze on the antipodes. Data on these matters are collected by many different agencies around the world, and collated by the World Meteorological Organisation in Geneva. Every year WMO publishes regular bulletins on the ozone hole during the critical months, and recently they published the findings for the current year.
Earlier this month the ozone hole extended over 25 million sq km an area 2 1/2 times the size of Europe from the Atlantic to the Ural Mountains. This makes it the largest ozone hole ever observed, beating the previous record of 22 million sq km in 1993 by a comfortable margin.