COLOMBO, Sri Lanka — Recognising the need to eliminate any remaining weaknesses in the international regime for protecting the earth’s ozone layer, governments will meet here from October 16 – 19 in order to strengthen the effectiveness of the Montreal Protocol on Substances That Deplete the Ozone Layer.

“Despite the enormous cuts in ozone-depleting chemicals achieved under the Montreal Protocol, the stratospheric ozone layer remains in poor health as a result of past emissions,” said Klaus Toepfer, executive director of the United Nations Environment Programme (UNEP), under whose auspices the 1987 Protocol was adopted.

“To minimise the damage to humans and the environment caused by increased ultraviolet (UV-B) radiation reaching the surface, we need to tackle simultaneously all the remaining sources of these chemicals,” he said.

While smaller than last year’s record thinning, the current spring ozone “hole” over Antarctica measures 24 million square miles — almost the combined size of the Russian Federation and Brazil. Earlier this year, during the Northern Hemisphere spring, the ozone layer over the Canadian Arctic declined by 20 per cent for a short time, while over Northern Siberia the decline exceeded 30 per cent in early March. Declines of 10 to 12 per cent were measured over large areas of densely settled Europe, and declines of six to 10 per cent were recorded over North America.

The Colombo meeting will consider accelerating the ozone layer’s revival by:

* Helping governments to comply with the agreed phase-out schedules.

* Discouraging the development and marketing of new ozone-depleting substances.

* Clamping down on illegal trade in CFCs and other substances.

* Promoting alternatives to ozone-depleting chemicals.

Related issues on the agenda include reducing emissions from ozone-depleting chemicals used as process agents (chemical catalysts), developing national management plans for reducing Halons in critical uses (such as fire-fighting) and considering critical-use exemptions for methyl bromide to be implemented beginning 2005.

The issue raised previously by the European Community regarding the tightening of the Protocol’s phase-out schedule for developing country consumption of HCFCs — a leading substitute for CFCs — will also be discussed at the meeting. The proposal by the European Community is based on the concern that, while much less destructive to the ozone layer than CFCs, HCFCs do contribute to ozone depletion, and alternatives are now available on the market.

Under the 1987 Montreal Protocol and its subsequent Amendments, governments have agreed to phase out chemicals that destroy stratospheric ozone, which is essential for shielding humans, plants, and animals from the damaging effects of harmful ultraviolet light.

Recent years have seen record thinning of the ozone layer, including an ever-larger ozone “hole” over Antarctica. Scientists predict that the ozone layer will start to recover in the near future and will fully recover some time in the mid-21st century, but only if the Protocol continues to be vigorously enforced.

However, they also believe that climate change (which is warming the earth’s surface but cooling the stratosphere and thus accelerating the chemical processes that lead to ozone depletion) may contribute to delaying the recovery.