The familiar message that recovery of the ozone layer could occur by the middle of the next century was repeated this summer in a report by the UN Environment Programme (UNEP) and World Meteorological Organization. 1 The assessment, their first since 1994, reported lower rates of increase in bromine and a decline in chlorine concentrations in the troposphere, and concluded that the abundance of ozone-depleting chemicals in the stratosphere would peak by 2000.
However, the record ozone hole observed over Antarctica in recent months - the widest, deepest and earliest to appear since records began - was accompanied by reports from the US National Oceanic and Atmospheric Administration and the National Aeronautics and Space Administration that global warming is contributing to ozone depletion.
As greenhouse gases build up in the lower atmosphere, they trap heat near the Earth's surface, reducing the amount of heat that rises into the stratosphere. Cooling of the stratosphere encourages the formation of polar stratospheric clouds, within which ozone destruction largely occurs.
Because ozone absorbs ultraviolet radiation from the sun - a process that heats the stratosphere - a vicious circle develops, with temperatures in the stratosphere dropping further as the amount of ozone declines. Some scientists now predict that ozone depletion in the stratosphere will continue for another 20-50 years before recovery some 75 years hence.
Moreover, the use of "ozone-friendly" HFCs and PFCs as replacements for CFCs and HCFCs is encouraged under the Montreal Protocol even though they are potent greenhouse gases and are included in the "basket" of six gases targeted by the Kyoto Protocol on climate change.
As a result, the tenth ministerial meeting of parties to the Montreal Protocol in November decided to make policies to protect the ozone layer consistent with controls on HFCs and PFCs. A workshop will be held with the Intergovernmental Panel on Climate Change (IPCC) to establish information on ways of limiting emissions of the gases. Ten days earlier, parties to the Kyoto Protocol, meeting in Buenos Aires, adopted similar decisions calling for co-ordination with the Montreal Protocol.
"For the first time we are seeing the emergence of an integrated approach to the global atmosphere," said UNEP's Executive Director, Klaus T”pfer. "We need to ensure that the scientific and policy responses underlying the two most important agreements on the global atmosphere - the Montreal Protocol and the Kyoto Protocol - are mutually supportive and fully co-ordinated."
Specific international controls on HFCs and PFCs could eventually emerge. In a press briefing issued prior to the Kyoto and Montreal Protocol meetings, HFC producer ICI welcomed the joint study with the IPCC "as an opportunity to demonstrate - yet again - how good HFCs are compared to other CFC alternatives." But it added that "even the perception that HFCs are to come under further government scrutiny will be enough to cast yet more doubt over their future and encourage further delays in the move away from CFCs whilst the study is in progress."
A note of caution was also sounded by a recent survey of production and consumption of ozone-depleting substances by the German Agency for Technical Cooperation (GTZ). 2 Previous calculations of future chlorine and bromine loading of the atmosphere may have been too optimistic, it warned, with consumption of ozone-depleting substances appearing to be much higher than assumed by UNEP's 1994 scientific assessment of ozone layer depletion.
Developing countries must freeze their production and consumption of CFCs and halons at average 1995-97 levels by next July, with eventual elimination by 2010. But, says GTZ, production and use of CFCs and halons have "increased significantly" in developing countries, overtaking industrialised nations in 1996. A growing portion of consumption in developing countries is being met by rapidly rising indigenous production, particularly in India and China - the latter holding more than 30% of the global total of production of ozone-depleting chemicals, having trebled its output since 1989.
China has also been identified by the Environmental Investigation Agency as the main source of illegal halons and CFCs smuggled into the EC and the USA under the guise of recycled or stockpiled material. 3 The material is allegedly being supplied to heavy industry and military end users in several EC countries, including the UK.
The measures agreed in Cairo included:
In addition, new measures, including labelling, were agreed to limit the export of new and used products and equipment, such as refrigerators, which require CFCs. A list of items which each country does not wish to import will be maintained and circulated by the Protocol secretariat.
Parties agreed to the adoption of national or regional management strategies in developed countries by July 2000 which will "consider" a deadline for complete decommissioning of non-critical installations and equipment. The strategies must also include measures to discourage the use of halons in new equipment and promote alternatives.
Parties agreed "actively" to discourage the production and marketing of bromochloromethane. Two specialist panels will assess whether n-propyl bromide, and other substances with a very short atmospheric lifetime of less than one month, pose a threat to the ozone layer. They will also seek to identify the sources and availability of halon 1202.
Parties will also report any new ozone-depleting substances being sold or produced in their territories to the secretariat "as far as possible" by the end of 1999, while the Protocol's legal drafting group will report back next year on ways of introducing controls on these chemicals.