Ozone hole on way to recovery say scientists

Posted: 19 September 2002

The world is making steady progress towards recovery of the ozone layer and should prevent a similar hole appearing in the Arctic to that in Antartica, says a new scientific report.

Monthly average ozone in September 2001, showing hole over Antactica. Credit: NASA.

The scentists warn, however, that the stratospheric ozone layer,while recovering from the effect of chemical emissions, will remain vulnerable during the next decade, even if governments comply with international agreements to protect it.

The preliminary four-year report, issued jointly by the UN Environment Programme and the World Meteorologcal Organisation in September 2002, shows that the total amount of ozone depleting chemicals in the lower atmosphere is continuing to slowly decline.

The authors of the report are nevertheless concerned on two counts. First, if the governments fail to meet targets laid down in the 1987 Montreal Protocol on Subsances that Deplete the Ozone Layer, this could delay or even prevent its recovery. There is also uncertainty about the links between ozone protection and climate change. The impact of greenhouse gases on the lower stratospheric zone could be "either positive or negative" the scientists say.

Harmful radiation

The ozone layer is essential to life on earth, shielding the planet from harmful ultraviolet radiation from the sun. More radiation would mean more skin cancers, eye cataracts, weakend immune systems and damage to ocean ecosystems, plants and microbes.

Presenting the report co-author Gerard Megie, said "The protocol is achieving its objectives. During the next decades, we should see a recovery of the ozone layer."

However, said Professor Megie, "the concentration of chlorine in the stratosphere has now reached a maximum and the ozone layer is still quite vulnerable. It is therefore extremely important that the control mesures in the Montreal Protocol are strictly respected by all." A worldwide agreement over 10 years ago banned the chemicals responsible for ozone destruction (mainly CFCs), but because of their longevity they are expected to go on damaging the ozone layer for decades.

Fifty years

Total recovery of the ozone layer to levels observed before 1980 will take at least 50 years, and expected changes in climate, including a cooler stratosphere, could delay this process.

Commenting on the Antartic ozone hole - which extends to three times the size of the United States at its full extent - the report notes that in the last decade it has increased in size, but not as rapidly as in the 1980s.

"It is not yet possible to say whether the area of the ozone hole has maximised. But they do think that "a future Artic polar ozone hole similar to the Antarctic appears unlikely."