Greenhouse gases could aggravate ozone loss and slow down recovery Increased atmospheric concentrations of global warming greenhouse gases (GHGs) could lead to more severe loss in the polar regions of ozone, the naturally occurring gas that filters out cancer- and cataract-causing ultraviolet (UV) rays from the sun, according to the United Nations World Meteorological Organization (WMO). While increased GHGs will lead to a warmer climate at the Earth’s surface, same increase is likely to lead to a cooling of the atmosphere at the altitude where the ozone layer is found, WMO said in a paper marking the Montreal Protocol’s 20th anniversary. Lower temperatures enhance the chemical reactions that destroy ozone. At the same time, the amount of water vapour in the stratosphere has been increasing at the rate of about 1 per cent per year. A wetter and colder stratosphere means more polar stratospheric clouds, which is likely to lead to more severe ozone loss in both polar regions. A cooling of the winter stratosphere over the last decades has indeed been observed, both in the Arctic and in the Antarctic, WMO noted, adding that these changes could delay the expected recovery of the ozone layer. The agency called on all nations with stratospheric measurement programmes to enhance them. It also urged funding agencies to support research on stratospheric ozone and harmful UV radiation. “Over the next 10 to 20 years, high-quality global observations of ozone and ozone-depleting substances will be particularly critical in verifying the effectiveness of actions taken under the Vienna Convention in 1985, the Montreal Protocol of 1987 and its amendments and adjustments,” said Mr. Michel Jarraud, Secretary-General of WMO. “As ozone-depleting substances reach a broad peak and slowly begin to decline, the search for recovery of ozone requires vigilance,” Mr. Jarraud cautioned Source: www.un.org Ozone hole over Antarctic appears early in 2007 A hole in the ozone layer over Antarctica has appeared earlier than usual in 2007, the United Nations weather agency said on recently. The World Meteorological Organisation (WMO) said it would not be clear for several weeks whether the ozone hole, which is expected to continue growing until early October, would be larger than its record size in 2006. While the use of ozone-depleting chlorofluorocarbons has waned, large amounts of chlorine and bromine remain in the atmosphere and would likely keep causing holes in the protective layer for years to come, WMO said. “Although ozone-depleting substances are now declining slowly, there is no sign that the Antarctic ozone hole is getting smaller,” it said in a report. The ozone hole may reach the southern tip of South America in 2007, according to Mr. Geir Braathen, a senior scientific officer with the WMO’s atmospheric research and environment programme. Source: www.reuters.uk.com  NASA will continue to keep an eye on ozone layer Scientists at the National Aeronautics and Space Administration (NASA), the United States, will join researchers from around the world this September to celebrate the success of the Montreal Protocol. Space-based instruments aboard NASA’s Aura satellite monitor the chemical make-up of the atmosphere and collect data that will help researchers better understand ozone chemistry through computer models. While the data show that average chlorine levels are declining, springtime ozone depletion in the polar regions continues to be a prominent atmospheric feature. Data from past satellite observations have been key to understanding ozone depletion. NASA’s Total Ozone Mapping Spectrometer (TOMS) was one of NASA’s signature ozone research achievements. “The TOMS images of the Antarctic ozone hole caused worldwide alarm and thus played a key role in the Montreal Protocol and other international agreements to phase out the offending chemicals from our environment,” said Mr. Pawan Bhartia, at the Goddard Space Flight Centre. In addition to the current satellite measurements, NASA research efforts use data collected on the ground, in the air and from previous missions. Scientists collect atmospheric composition data from ground-based monitoring stations around the world. Researchers have collected measurements since 1978 for compounds identified in the Montreal Protocol. The data come from coastal monitoring stations used in previous missions and as part of the NASA-sponsored Advanced Global Atmospheric Gases Experiment. For researchers working to predict the future of the global ozone layer, all these measurements are important. The differences between loss and recovery of ozone at the poles and in non-polar regions are complex. The focus in ozone research has now shifted to include the effects of climate change. “Twenty years ago we went out of our way to separate ozone depletion from climate change,” said Ms. Ross Salawitch, an atmospheric chemist at the Jet Propulsion Laboratory, California. “After a decade of looking at data, the community realizes they are linked in subtle but profoundly important ways.” Source: www.sciencedaily.com