Brussels, 11 Sep 2003
Researchers say the rate of ozone depletion in the Earth's upper atmosphere is slowing. Bans on harmful industrial gases may be having the desired effects after all.
A team of US scientists are putting the cat among the pigeons. In a study to be published in the Journal of Geophysical Research – Atmospheres, the researchers provide evidence that the ozone fragmentation occurring high above the Earth has been slowing since 1997, which goes against common-held beliefs that ozone depletion has continued unabated since it was first detected in the 1980s.
Together with his team, Professor Michael Newchurch, an atmospheric scientist at the University of Alabama, has studied data on atmospheric ozone and greenhouse gases collected from the National Aeronautics and Space Administration (NASA), a sponsor of the research, and several international ground stations.
The results indicate that ozone dissipation in the upper stratosphere, some 35-45 km above ground, is slowing, while ozone-destroying chlorine in that layer of the atmosphere is still increasing, but not as quickly as in the past. This, according to Professor Newchurch, is the first clear evidence that a worldwide reduction in chlorofluorocarbons (CFC) pollution is having the desired effect.
"This is the beginning of a recovery of the ozone layer," said Newchurch in a press statement. These findings indicate that the global problem of ozone destruction could be behind us. "We had a monumental problem of global scale that we have started to solve," he adds.
The 'hole' truth
According to the UN Ozone Secretariat (UNOS), ozone is very rare in our atmosphere, averaging about three molecules of ozone for every 10 million molecules, and plays an important role in shielding us from the sun's harmful ultraviolet light.
Ozone is found mainly in two regions of the Earth's atmosphere. "Most ozone (about 90%) resides in a layer that begins between 8 and 18 km … above the Earth's surface and extends up to about 50 km ...[the stratosphere]. The ozone in this region is commonly known as the ozone layer. The remaining ozone is in the lower region of the atmosphere, … the troposphere," notes the UNOS.
Every year since the worldwide ban on CFCs in 1987, new evidence of worsening ozone depletion has filtered out of the scientific community. The latest discovery tells us a different story, but Newchruch warns against jumping to conclusions.
"We are now at the point where the [CFC] restrictions are tight enough to result in a measured turnaround of CFC amounts at the [Earth's] surface. Now we can say that what we're doing is working and we should continue the ban," he asserts. "We're not gaining ozone, we're just losing it less quickly. But the trend line is flattening. And the increase of chlorine in that layer of the stratosphere has slowed significantly, so we should start to see some ozone improvement in the coming years."
The results and progress of EU-backed research into the ozone layer – the Theseo project – will be the subject of a conference in November this year. The European Commission supports many other scientific projects on ozone and climate. For details of EU-funded projects, consult the Projects Database on the CORDIS web server.