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Athens News Agency

June 17, 2004

HEADLINE: OZONE LAYER WILL REMAIN VULNERABLE IN COMING DECADES, SCIENTISTS STRESS AT MAJOR KOS SYMPOSIUM

Scientists attending the 20th Quadrennial Symposium on Atmospheric Ozone on the island of Kos from June 1-8, on the 20th anniversary since the discovery of the ozone hole above the Antarctic, warned that the ozone layer will remain vulnerable in the next decade or so, especially in the polar regions, even with full compliance with the Montreal Protocol

In a press release outlining the symposium's conclusions on Thursday, International Ozone Commission Secretary Prof. Christos Zerefos noted that the Montreal Protocol and its amendments had led to a fast decrease in the emissions of ozone-depleting substances, such as CFCs, but stressed that actual ozone recovery was harder to detect since it was influenced by complex atmospheric interactions and year-to-year climatic variations

Zerefos also reported forecasts in the 690 scientific papers presented at the symposium that UV-B levels in 2000-2019 will decrease for all seasons except spring in both hemispheres, though not by a statistically significant amount and with the exception of a region in western Europe, where UV-B is seen as rising due to a decrease in cloudiness

According to the data presented, emissions of ozone-depleting substances through human activity peaked in the last years of the 20th century and then decreased due to the Montreal Protocol. Continued compliance with the Protocol is expected to bring about a very slow decrease in stratospheric concentrations of ozone-destroying chemicals in the next decades

Measurements show a decline in ozone-depleting CFCs in the lower atmosphere and a levelling off of the chlorine content in the stratosphere. There are also overall indications that ozone is higher in recent years than expected but it is hard to say whether this is statistically significant, since a number of factors are known to affect ozone response, ranging from water vapour content and variability in weather patterns to greenhouse gases, radiation balance and volcanic explosions, such as that of Pinatubo and El Chichon in the early '80s and '90s

According to data collected during the more intensified global atmospheric monitoring since the discovery of the ozone hold, losses in total column ozone relative to pre-ozone-hole abundances of 1980 are around 3-4 per cent in northern midlatitudes in winter and spring and about 6 per cent in southern midlatitudes all year round

Scientists say that for coming decades the atmospheric abundances of ozone-depleting substances will be near their highest and human- influenced perturbations will be at or near their largest. They stressed that continued compliance with the Montreal Protocol is expected to lead to a recovery of the ozone layer

According to the IOC, a 70-year-old scientific body responsible for the science of the ozone layer, the detection of ozone recovery requires patience since there is still a long way to go before scientists fully understand the complex system of interactions between ozone and a globally changing environment

"The best tools we have at present are the continuation of global quality observations both from ground and from space," Zerefos notes in the press release

The topics discussed during the symposium included the search for ozone recovery in long-term data records of ozone, the use of satellite and ground-based data to evaluate models of ozone loss and recovery, the extension of long-term data records made by satellites or on the ground, evaluation of the future of ozone recovery in a changing climate using coupled climate/chemistry models, development of satellite capability to measure the content of the troposphere and measurements and trends in UV radiation levels reaching the earth's surface.

(C) Reed Elsevier Inc.

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