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Published: Monday 05 August, 2013

outdoor wear women outdoor wear women Earths ozone layer begins repairing itself News in Science AB outdoor wear women C Science

The rate of ozone destruction in the upper atmosphere is slowing, suggesting for the first time the global ban on the production and release of damaging industrial gases is having an effect.

A team led by Professor Michael Newchurch, an atmospheric scientist at the University of Alabama in Huntsville, USA, analysed measurements of atmospheric ozone and greenhouse gases taken from three NASA satellites and three international ground stations.

They found that ozone depletion in the upper stratosphere the layer of the atmosphere between 35 and 45 km above the ground has been outdoor wear women slowing since 1997. Their results are to be published in the Journal of Geophysical Research Atmospheres.

Ozone is a damaging pollutant near the ground, but in the stratosphere, it shields the Earth from harmful ultraviolet radiation from the Sun and cosmic rays from space, all of which can cause skin cancers.

In the 1980s, scientists detected for the first time an ozone hole forming over Antarctica each August, eventually breaking up by December or January. Another hole was discovered over the Arctic both regions vulnerable to ozone damage.

Scientists eventually showed that chlorine released in the upper atmosphere from chlorofluorocarbons, or CFCs chemicals used as refrigerants and aerosol propellants were destroying this ozone layer. The three scientists Mario Molina, F. Sherwood Rowland, and Paul Crutzen jointly won the 1995 Nobel Prize in Chemistry for their finding.

Released into the atmosphere, CFC molecules percolate into the upper atmosphere. As they rise, ultraviolet light breaks them up, releasing chlorine which outdoor wear women goes on to break ozone molecules down to its constituent oxygen molecules.

The discovery eventually led to an international ban on CFCbased products, a ban which Newchurch said his findings show is paying off. We can say that what were doing is working, and we should continue the ban on CFCs, he said. But there is still cause for concern, he added.

Ozone is still being lost from the stratosphere. And the amount of chlorine the chemical that which does the damage in that layer of the stratosphere has not yet peaked, though it has slowed down significantly.

When chlorine levels do peak and then begin to fall, ozone levels should continue to rise, said Newchurch. However, the amount of ozone in the upper stratosphere where the rate of loss is slowing is small compared to the total amount of ozone in the stratosphere as a whole.

We dont see compelling evidence that the destruction of ozone is slowing in the lower stratosphere, where 80% of the protective ozone layer exists, said Newchurch.

In the lower stratosphere, the layer of atmosphere between about 20 and 35 km up, the threat to the ozone layer comes not just from chlorine but also from greenhouse gases such as carbon dioxide and methane.

Best known for their warming effect on the lower atmosphere, these greenhouse gases have the reverse effect on the stratosphere, said Newchurch. Here, they radiate heat out to space, cooling the lower stratosphere.

This cooling changes wind and air mixing patterns in a way that can increase ozone depletion, especially at high latitudes although the effect tends to be mitigated in part by the fact that cooling slows the rate at which ozone is degraded into oxygen so cooling has both good and bad effects on ozone depletion.

Unfortunately, it is proving easier to ban aerosols and refrigerants containing CFCs than to impose meaningful greenhouse gas emission restrictions on an energyhungry world, he commented. space agency.. outdoor wear women