What is ozone? How did researchers discover its role in Earth's
atmosphere and the devastating consequences of its depletion?
Significantly enough, depletion of ozone levels has been recorded around the globe.
Like an infection in the body that grows more and more virulent, the continent-size hole in Earth's ozone layer keeps getting bigger and bigger. Ozone (O3) is one of the naturally occurring trace gases that make up our
atmosphere. Earth’s atmosphere serves three critical functions: it provides life-giving oxygen, keeps the earth warm, and protects us from deadly ultraviolet (UV) radiation from the sun. Most of the atmosphere consists of nitrogen and oxygen, in the air we breathe. These gases do not hold heat so they do not keep us warm. They also do not protect the earth from UV rays. For those functions you have to turn to trace gases found in the atmosphere, commonly referred to as
greenhouse gases. They are: water vapor, carbon dioxide, methane, ozone and nitrous oxide. These trace gases function like the transparent covering of greenhouse gases which are: water vapor, carbon dioxide, methane, ozone and nitrous oxide.
The trace gases function like the transparent covering towards “greenhouse effect”. Ozone is a particularly critical trace gas because it plays two roles. In the low atmosphere, it adds to the greenhouse gases, keeping the earth warm. But it serves a more critical protective function in the upper atmosphere where it blocks nearly all of the sun’s deadly UV rays from reaching the earth.
UV rays are associated with many causes of skin cancer. The UV index is used in summer to let people know how long it would be safe to stay in the sun. A decrease in the ozone correlates to an increase in skin cancer in people. This is an important index because ozone has been in a steady rate of depletion and now there are holes in the upper ozone layer.
The holes were first discovered in 1985 over Antartica where atmospheric circulation, temperature and other factors “draw” holes to that region. The Antarctic hole now measures about 9 million square miles, nearly the size of North America. Less dramatic, still significant, depletion of ozone levels has been recorded around the globe. Discovery of the depleted ozone holes created a worldwide concern and worry over how the ozone layer should be protected.
The main culprit was human-produced chlorofluorocarbons (CFC’s).Very small amounts of CFC gas can destroy enormous amounts of ozone. CFC’s have been released into the atmosphere for years. They are emitted in part from aerosols made with CFC propellant, refrigeration units and air conditioners. As the CFC’s reach the upper stratosphere, UV rays cause the gas to release free chlorine atoms. It only takes a single chlorine molecule to cause tens of thousands of ozone molecules to break down into simple oxygen. And oxygen does not filter UV rays.
The move to ban CFC’s was slow but all major countries producing them phased them out by the year 2000. The CFC’s already released will take another estimated 50 years to break down, and CFC’s will continue to be released by old products still in use.
As a result, ozone levels and the hole over Antartica continue to be monitored closely. In addition to being naturally occurring gas, ozone is also created in the burning of fossil fuels as one component of smog. Burning fossil fuels also releases carbon dioxide into the air, thickening greenhouse gases, adding to the greenhouse effect and global warming.
Important websites:
http://www.beyonddiscovery.org/content/view.article.asp?a=73
http://greennature.com/article592.html
http://www.epa.gov/ozone/science/
http://www.atm.ch.cam.ac.uk/tour/