WASHINGTON - Increases in the ozone-destroying chemical CFC-12 in the upper atmosphere are slowing, German researchers report.
"The CFC-12 data show a continuous and rather constant increase between 1978 and the early 1990s, while a slowing down of the trend is observed after about 1990," the scientists report in a paper scheduled to appear in the Sept. 1 edition of Geophysical Research Letters. CFC-12, a chlorofluorocarbon once commonly used in refrigerators and air conditioning systems, is one of the main chemicals found to be damaging the ozone layer in the upper atmosphere.
The high-altitude natural ozone layer forms a barrier against ultraviolet radiation from the sun. Excessive levels of UV radiation cause skin cancer in humans and can damage many plants and animals.
The depletion has been particularly severe over the Antarctic, where it gained the designation "ozone hole."
Fears that severe ozone depletion could spread to populated areas of the world led to the 1989 Montreal Protocol in which countries agreed to reduce or eliminate ozone-damaging chemicals.
Although 165 countries have agreed to that protocol, levels of CFC-12 continued to increase as the gas escaped from equipment still in use.
The slowing of those increases, the new paper reports, confirms that the Montreal Protocol has become effective, though it will take years to reduce CFC levels because the chemical can remain in the air 10 to 15 years.
The study was done by Andreas Engel and Ulrich Schmidt of Johann Wolfgang Goethe University in Frankfurt and Daniel McKenna of the Institute for Stratospheric Chemistry in Julich, Germany. Geophysical Research Letters is published by the American Geophysical Union.
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