The latest Assessment NAIROBI/GENEVA, 6 September 1994 (UNEP) -- A panel of 226 of the world's leading atmospheric science experts have issued an assessment of the state of current understanding of ozone depletion, indicating that international efforts to reduce the impact of ozone depleting substances are having their desired impact. In spite of these control measures, which will gradually improve the state of the ozone layer during the next century, record low global ozone has been observed during the past few years, and the ozone layer's most vulnerable period still lies ahead.

The Executive Director of the United Nations Environment Programme (UNEP), Ms. Elizabeth Dowdeswell, noted that "the international community has relied on these periodic scientific, economic and technological assessments in order to adapt to rapidly evolving conditions. While the 1994 Assessment Panel report confirms that we are heading in the right direction, we cannot afford to be complacent. The line that divides complacency from catastrophe is very thin and now is not the time to break that momentum."

Under the international auspices of the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), the Panel's 1994 findings are the latest in a series of such scientific assessments mandated by Article 6 of the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer.

Some of the key findings of the 1994 Assessment are:

CFC build-up in the Stratosphere has slowed

* The rates of build-up in the atmosphere of human-made compounds that deplete the ozone layer (e.g., chlorofluorocarbons (CFCs) and halons) have slowed in recent years as a direct result of reductions in global emissions of these compounds. These demonstrate that the Montreal Protocol and its Amendments and Adjustments are reducing the impact of anthropogenic halocarbons on the ozone layer and should eventually eliminate ozone depletion.

Peak Global Ozone Depletion will Continue until 1998

* The peak global ozone depletions are expected to occur during the next several years. The ozone layer will be most affected by human-influenced perturbations and most susceptible to depletion around the year 1998. Then, after 1998 the levels of ozone- depleting chlorine and bromine are expected to slowly decrease and the ozone layer is expected to recover in about 50 years in response to planned international actions.

Record Depletion in 1993 due to Man + Pinatubo

* Record low global ozone has been observed over the past two years, with the most severe Antarctic ozone "hole" and lowest seasonally averaged ozone over populated regions of the northern hemisphere ever measured. This record depletion was probably due at least in part to temporary enhancements in ozone's vulnerability to human-made chlorine and bromine related to chemical processes linked to the 1991 eruption of Mt. Pinatubo in the Philippines.

Methyl bromid now a factor

* Methyl bromide continues to be viewed as a significant ozone- depleting chemical. Three potentially major human sources of atmospheric methyl bromide have been identified (soil and post- harvest fumigation, biomass burning, and exhaust of automobiles using leaded gasoline) in addition to the natural oceanic source. The best estimate for the ozone depletion potential (ODP) of methyl bromide is 0.6 (i.e, it destroys 60% as much ozone per kilogram emitted as does CFC-11).

Reduce methyl bromide and hydrochlorofluorocarbons; total recaputure of CFCs and ahlons

* Approaches to lowering future stratospheric chlorine and bromine abundances are limited. Further controls on ozone-depleting substances are not expected to significantly change the timing or the magnitude of the peak stratospheric halocarbon abundances and hence peak ozone loss. However, four approaches are evaluated in this assessment that would steepen the fall from the peak halocarbon levels in the early decades of the next century: reductions in emissions of anthropogenic methyl bromide, reductions in emissions of hydrochlorofluorocarbons (HCFCs), complete recapture (as opposed to recycling) of CFCs banked in existing equipment, and complete recapture of halons in existing equipment. In addition, the delayed recovery of the ozone layer that could result from failure to adhere to the international agreements is also quantified in this study.

The 1994 Scientific Assessment, along with assessments on the environmental and health effects of ozone layer depletion and one on the technology and economic implications of mitigation approaches, are part of the information upon which the Parties to the Montreal Protocol will base their future decisions regarding protection of the stratospheric ozone layer.