A worldwide treaty banning aerosols 25 years ago averted a global catastrophe, New Zealand ozone layer scientists said yesterday.

Niwa scientists played a major role in creating the Montreal Protocol, signed a quarter of a century ago tomorrow and widely hailed as the world's most successful international environmental protection treaty which banned CFCs. The agency yesterday said that given New Zealand's location, world-class research scientists and instrumentation, its contribution to the treaty had been profound.

Niwa atmospheric scientist Dr Olaf Morgenstern, as well as other international scientists, has run atmospheric models for a non-intervention, no-Montreal Protocol scenarios.

It shows that at the end of the 21st century the ozone layer is nearly completely wiped out, bringing widespread skin cancer and food shortages.


"In this sense, the Montreal Protocol took effect just in time to avert a catastrophe," Dr Morgenstern said.

And New Zealand scientists have continued to lead the world in monitoring the ozone layer, with Niwa's Lauder station in Central Otago specialising in measuring CFCs, ozone and UV light levels.

A University of Canterbury atmospheric researcher this week revealed that New Zealand's ozone hole - responsible for a 14 per cent jump in melanoma over the past decade - is shrinking for the first time in 30 years.

"Ozone levels above Antarctica are projected to return to 1980 levels - previous to the ozone hole - after 2050," said Dr Adrian McDonald.

"It was after the discovery of the ozone hole over Antarctica by the British, in 1985, that people began to be more interested in getting something done," said Niwa principal scientist Dr Richard McKenzie.

"Our measurements in Antarctica helped the community focus on the CFC issue, rather than on an alternative theory which attributed the ozone hole to variations in solar activity."