Ozone, which in natural conditions comprises less than one part per million (ppm) in the atmosphere is 90% concentrated above 10 km in altitude. The ozone layer protects the Earth and its fauna and flora from harmful levels of ultra-violet solar radiation, by filtering it down to acceptable levels for life. Too great an exposure to ultra-violet rays causes skin cancer and eye cataracts on animals and humans, yield losses in crops, and destroys the phytoplankton that underlies the marine food chain.
In 1985, scientific findings established that ozone levels over Antarctica between September and November had fallen by 50% since the 1960s. The Antarctic 'ozone hole', which has appeared over the Antarctic every southern spring, covered an area in September 1995 of 10 million square km, twice the area of the previous year, approximately 2% of the surface of the planet – the size of Europe. Subsequent findings suggest that ozone depletion has spread around the planet's stratosphere, and has become a global phenomenon. In 1995, WMO reported ‘unusually low’ levels over the northern hemisphere. Siberia was the worst affected, with 35% depletion. Between October 1994 and March 1995, the average loss over Europe was 11%, and over North America 7%. In March 1995, the Arctic recorded depletion for the first time, at 25%. The greatest ozone depletion recorded to date over a populated area was over a town in Argentina. Recent UNEP scientific reports conclude that “reductions in stratospheric ozone are continuing, both in the Antarctic with the reappearance of the ozone ‘hole’ each spring, and at other locations and times in both hemispheres”, and that “new concerns have been raised by record low ozone, and associated higher UV-B radiation at the Earth’s surface, over populated areas of the northern hemisphere during late winter and early spring”. One finding in 1997 reported a 20% reduction over the Arctic in March 1997 from the previous year.
The threat was officially recognised by the international community
in the context of the early negotiations for the 1985 Vienna Framework
Convention for the Protection of the Ozone Layer which records an awareness
of the “potentially harmful impact on human health and the environment
through modification of the ozone layer”.
The global objective and strategy
The vital planetary interest lies in an early reduction and total phase-out of all ozone-depleting substances (ODS). The international community recognized the global objective, in response to that threat, as “protect[ion of] human health and the environment against adverse effects resulting from modification of the ozone layer”. Such adverse effects meant changes in the physical environment or biota, including changes in climate, which have significant deleterious effects on human health or on the composition, resilience and productivity of natural and managed ecosystems, or on materials useful to humankind.
Over a period of four years from March 1981 to March 1985, negotiations were completed on a framework convention on ozone depletion. Shortly thereafter and within a nine-month period from December 1986 to September 1987, negotiations were completed on a protocol to the Convention that restricted national production and consumption of ozone-depleting substances. In terms of traditional diplomatic action, this is rapid work by the international community.
The global strategy for attaining the above objective was identified in the 1987 Montreal Protocol, ratified by 163 countries by December 1997. Essentially, the strategy involves “precautionary measures to control equitably total global emissions of substances that deplete it [the ozone layer], with the ultimate objective of their elimination on the basis of developments in scientific knowledge, taking into account technical and economic considerations.” The negotiations revolved largely around agreeing on what was ‘equitable’ in this context.