Ozone layer recovering more slowly than expected, finds report
The ozone layer is on the mend but holes will take longer than previously expected to close, according to the World Meteorological Organisation (WMO) and the United Nations Environment Programme (UNEP). The findings come from a summary of a report to be published in 2007 on the effects of the 1987 Montreal Protocol, which committed signatory nations to progressively banning the use of ozone-harmful products. The ozone layer blocks harmful ultra-violet rays. Its depletion has been blamed for increased risk of skin cancer in humans, as well as damage to plants, and reduction of plankton populations in the sea. The shrinking ozone is caused by the chemical action of chlorine and bromine released by man-made chlorofluorocarbons (CFCs), which are used in aerosol sprays and cooling equipment, like refrigerators and some air-conditioning systems. Prepared by 250 international scientists, the report concludes that the ozone layer over the Antarctic should recover by 2065, 15 years later than previously expected. Because of special conditions within the Antarctic vortex - a natural cyclone of super-cold and fast winds - the ozone-depleting gases take longer to be removed. Similarly the ozone layer over the mid latitudes of the Northern and Southern Hemisphere will take up until 2049 to recover, according to the scientists - five years later than anticipated by a previous assessment made in 2002. The latest assessment is based on upward projections of the levels in the atmosphere of certain types of chlorofluorocarbons (CFCs), which have yet to be banned under the Montreal Protocol and are still found in refrigerators and other equipment. Scientists also estimate that the future production levels of hydrochlorofluorocarbons (HCFC-22), a CFC substitute, while much safer, will still cause some ozone depletion. 'While these latest projections of ozone recovery are disappointing, the good news is that the level of ozone-depleting substances continues to decline from its 1992-94 peak in the troposphere and late 1990s peak in the stratosphere,' said Michel Jarraud, Secretary-General of WMO. This decline in ozone-depletion is mainly due to the early removal of shorter-lived gases such as methyl chloroform and methyl bromide. 'But the delayed recovery is a warning that we cannot take the ozone layer for granted and must maintain and accelerate our efforts to phase out harmful chemicals,' said Achim Steiner, Executive Director of UNEP. The report evaluates some of the options for accelerating the ozone layer's recovery, as well as circumstances that could delay recovery. It concludes that the hypothetical elimination from production and existing equipment of CFCs, halons, HCFCs, methyl bromide, carbon tetrachloride and methyl chloroform by the end of 2006 would advance recovery at mid-latitudes by 15 years to 2034. This goes beyond the Montreal Protocol, the signatories of which agreed to gradually phase out all CFC use and production, including HCFCs, by 2030.