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Chemicals ban is leading to recovery of ozone layer

Science Editor,Steve Connor
Saturday 02 August 2003 00:00 BST
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Scientists have found evidence that the Earth's protective ozone layer is beginning to heal after the enforcement of an international treaty banning CFC chemicals.

Measurements from three satellites and three ground stations have confirmed that the rate of ozone depletion in the upper atmosphere has slowed down significantly during the past decade, according to a study by the American Geophysical Union.

But Professor Michael Newchurch, an atmospheric scientist at the University of Alabama in Huntsville, said that it would take at least another 50 years before the ozone layer completely recovered.

The scientists attribute the success to a decision taken in Montreal in 1987 to phase out the production of chlorofluorocarbons (CFCs) in products such as aerosol sprays and refrigerators. Chlorine in CFCs destroys the ozone layer.

Professor Newchurch said that the study analysed ozone concentrations in the upper atmosphere - an altitude of about 40km - because this was expected to be most sensitive to the reduction in the CFCs.

"[Ozone] has been declining at about 8 per cent per decade for a couple of decades, and now it's only about 4 per cent per decade," he said.

"Even though we've seen the first stages of recovery, it's absolutely essential that we don't produce these chemicals again. Ozone is still going down, it's just that it's not going down as fast as it has been," he said.

Ozone screens the ground against harmful ultraviolet light from the sun and is essential for much of life on Earth. The gas - composed of three atoms of oxygen - is produced and destroyed naturally but an equilibrium can be achieved in an unpolluted world.

But chlorine in CFCs caused greater destruction, which largely takes place over polar regions at the end of the long Arctic and Antarctic winters, when sunshine causes photochemical reactions.

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