for National Geographic News
Damage to the ozone layer, caused by chlorofluorocarbon (CFC) chemicals and other pollutants, may be starting to reverse itself according to data collected by NASA satellites.
While ozone degradation continues despite global bans on ozone-depleting pollutants imposed more than a decade ago, the rate has slowed markedly enough in one layer of the atmosphere that scientists believe ozone could start to be replenished there within several years.
"There is compelling evidence that we are seeing the very first stages of ozone recovery in the upper atmosphere," said Michael Newchurch, an atmospheric chemist with the National Space Science and Technology Center at the University of Alabama in Huntsville.
Evidence suggests that international efforts to reduce chlorofluorocarbon (CFC) pollution are working. However, Newchurch cautioned that those efforts not be curtailed. "It is absolutely essential that we continue not producing these [ozone-depleting] substances for the rest of the time we want to live on this planet," he said.
Newchurch led the scientific team who will reveal their finding in an upcoming edition of the Journal of Geophysical Research.
Enormous Ozone Hole
Though ozone is only present in tiny quantities in the atmosphere, it is essential to life, as it absorbs harmful ultraviolet (UV-B) light. The ozone layer cuts out up to 95 percent of the sun's UV-B radiation, said Newchurch. Increases in skin cancer cases have been recorded in parallel with ozone depletion. UV-B rays can also cause cataracts and damage crops.
The majority of atmospheric ozone (the "ozone layer") is found in the stratosphere, the region of the atmosphere found six miles (ten kilometers) above the Earth's surface and beyond.
In the mid-1970s, Scientists first noticed that chlorine produced in the atmosphere from human-made CFCs and similar chemicals had the potential to destroy ozone and damage the ozone layer. CFCs were previously used in refrigerators, fire extinguishers, air conditioners, and as aerosol propellants in a wide-range of spray can consumer products, from paint to deodorant to hair spray.
Observations then showed that CFC chemicals were building up in the atmosphere and that the ozone layer was thinning. The most dramatic discovery came in the mid-1980s: Scientists with the British Antarctic Survey discovered the enormous ozone hole which appears seasonally, exposing the entire Antarctic continent to levels of ultraviolet radiation many times greater than natural levels.
As a result of these findings, and their grave implications, governments came together to produce the 1987 United Nations Montreal Protocol. "A life-saving step for the planet," said Newchurch. This treaty and subsequent amendments led to the development of replacement chemicals, and a near-total ban on the use of CFCs and related chemicals.
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