Antarctic ozone damage at record levels

OZONE destruction over the Antarctic reached record levels last month, the United Nations' World Meteorological Organisation (WMO) said yesterday.

It believes this year's 'hole' could be the widest and deepest to date - a finding that surprised British Antarctic Survey scientists who had thought there would be a slightly smaller hole due to the fading influence of two huge volcanic eruptions in 1991.

Godwin Obasi, head of the WMO, said the data showed there was no room for complacency despite the relative success of international efforts to phase out destructive industrial chemicals.

The ozone is found, heavily diluted, in a broad band of the upper atmosphere 30,000 ft above the entire globe. It absorbs ultraviolet light that can cause skin cancers and harm crops and plankton.

A 'hole' occurs when ozone levels are cut by more than half. This has happened above the Antarctic each spring for the past decade. A combination of sunlight, high- level ice clouds, stable atmospheric conditions and a critical level of man-made chlorine and bromine create perfect conditions for ozone destruction.

Scientists believe two huge volcanic eruptions, Mount Hudson in Chile and Mount Pinatubo in the Phillipines, exacerbated ozone destruction by injecting sulphur dioxide into the upper atmosphere.

Monitoring stations in the Antarctic, including two British Antarctic Survey bases, recorded ozone depletion of up to 65 per cent last month. Satellite observations show a 70 per cent depletion taking place two weeks earlier than in previous years.

Jonathan Shanklin, a meteorologist with the Cambridge-based survey, said: 'The hole has come earlier and preceded more rapidly. We were expecting things to be not quite so bad this year.' The zone of ozone depletion covered the southern tip of South America.

The depletion peaks in early October and levels of the gas then build up again over the next few months. Ozone destruction also happens over Arctic regions in the northern hemisphere in spring, but never to the same extent as around the South Pole. This year the Arctic ozone suffered less damage than in the two previous years, almost certainly because of the fading influence of the volcanic eruptions.

The use of ozone-destroying chlorofluorocarbons (CFCs) should be banned in developed countries at the end of this year under the Montreal Protocol. But there are concerns about a continuing black market in the chemicals, which are used in refrigeration and air conditioning. A variety of other chlorine-containing chemicals which harm ozone are also being phased out.

Because CFCs break down very slowly, chlorine levels in the upper atmosphere continue to rise even as production is wound down.

Around 2000, the concentration of chlorine in the upper atmosphere should start to fall. The ozone layer should then begin to restore itself, although holes are expected to appear each spring above the Antarctic for several decades. A spokesman for the Department of the Environment said: 'The scientists had warned us that things would get worse before they got better .'

There is pressure for another round of tougher Montreal Protocol restrictions on chlorine-containing chemicals. It would be the fourth in less than 10 years. Each time, the phase-out dates have been brought forward as understanding of the threat has grown.