ES&T EUROPEAN N E W S
HCFCs May Slow Ozone Layer Recovery
T
he 1992 agreement to phase out chlorofluorocarbon (CFC) p r o d u c t i o n by the end of 1995 has been heralded as a success for international environmental diplomacy. Signed in Copenhagen under the Montreal Protocol, the 1992 agreement also brought the socalled "transitional substances," hydrochlorofluorocarbons (HCFCs), under international regulation for the first time. However, according to a recent report, the new HCFC caps will delay the recovery of the ozone layer by up to eight years. The physical properties of HCFCs and their low toxicity make them good replacements for CFCs in many applications, including refrigeration. Their long-term impact on the ozone layer is less than 15% that of the old CFCs, sometimes less than 5%. Unfortunately, however, the new chemicals' short-term and mediumterm impact can be significant. During the first 20 years after release into the atmosphere, some HCFCs destroy 37% as much stratospheric ozone as would CFCs. To the dismay of environmental groups, the revised Montreal Protocol permitted the use of HCFCs in large volumes until 2015, and in smaller volumes thereafter up to an eventual phase-out date of 2030. Nevertheless, there is a cap on the total amount of HCFCs the chemical industry will be allowed to manufacture. Under the protocol, annual production is capped so that the HCFCs' total ozone depletion potential does not exceed 3.1% of that caused by CFC emissions in 1989. According to a report (2) by a panel of British scientists, published in January, HCFC emissions at the Copenhagen levels will delay ozone layer recovery. The report is the fifth in a series by the Stratospheric Ozone Review Group (SORG), set up by the British government in 1985. SORG is currently chaired by John Pyle of the University of Cambridge, who is also director of the European Ozone Research Coordination Unit.
BY J U L I A N
ROSE
In the new report SORG draws together the latest ozone layer research published in the scientific literature or reported by research teams. With the exception of chlorine loading caused by future HCFC emissions, the picture is encouraging. The actual consumption of CFCs has been lower than forecast in 1991, when SORG last reported. The result is that chlorine loading in the atmosphere will return to 1990 levels two years earlier than predicted by SORG in 1991. In addition, the speedier phase-out of CFCs, under the 1992 revision of the Montreal Protocol, will cut this recovery time by a further two years. The net effect is that, with no HCFC emissions, chlorine loading would return to the 1990 level—just over 3.5 parts per billion by volume—by 1998. By 2100, loading would fall to about 1.3 ppb, still twice the natural concentration. If HCFCs are brought into the picture, however, the recovery of the atmosphere is delayed, and the peak chlorine loading is 3.9 ppb rather than 3.7 ppb without HCFCs. The report concludes: "If HCFCs were used at the full rate permitted by the 3.1% cap, this could extend the time to return to 1990 levels of chlorine loading by up to eight years." Beyond 2050, however, the impact of the chemicals will not be noticeable, because HCFCs have a comparatively short atmospheric lifetime. SORG's calculations assume, perh a p s over-pessimistically, that chemical firms will make use of their full allocations of HCFC production u n d e r the Copenhagen agreement. But, in the case of Western Europe, the group takes into account the new European Union (EU) regulation on ozone-depleting substances. The new EU law tightens the terms of the Copenhagen agreement. The 3.1% cap is cut to 2.5% for EU countries, and a full HCFC phase-out is required by 2015. The effect: in 1996 almost a fifth of
0013-936X/94/0927-111A$04.50/0 © 1994 American Chemical Society
world HCFC production will be in EU countries; by 2004 the EU will account for only one-tenth. Clearly, the picture will change as other countries pass laws to accelerate HCFC phase-out and, perhaps, the Montreal Protocol is revised yet again. As well as looking at chlorine loading, SORG reviewed the latest ozone layer research. Since 1979, the group reports, there has been a 3% per decade fall in average ozone concentrations in the mid-latitudes of both hemispheres. Because chlorine loading is set to increase for most of this decade, ozone losses are expected to get worse before recovery takes place. In a widely reported 1990 measurement, in the mid-latitudes of the northern hemisphere, springtime ozone levels were down 8% from those of 1975. More recent observations have detected Arctic concentrations of the chlorine monoxide radical that are on occasions higher than those found over Antarctica, and there is strong evidence of chlorine-catalyzed ozone destruction. Given the right weather patterns, therefore—a very cold spring and strong winds forming a polar vortex that prevents replenishment with ozone-rich air—one might expect an Antarctic-style ozone hole to develop in the north. But the 1991 eruption of Mount Pinatubo has blurred the picture. Sulfuric acid aerosols from volcanoes cause ozone depletion that adds to the effect of anthropogenic pollution. SORG concludes that it is not yet possible to say how much of the northern hemisphere ozone decline is a result of the Pinatubo eruption and how much is caused by chlorine. Reference (1)
Stratospheric Ozone Review Group. Stratospheric Ozone 1993. Available from HMSO Books, London, England; about $9.00; fax orders: 44 71 873 8200; phone: 44 71 873 9090.
Julian Rose is an environmental and technology writer based in London.
Environ. Sci. Technol., Vol. 28, No. 3, 1994 111 A
