CFC gases

The depletion of the ozone layer increases by the catalysis of chlorofluoro carbon (CFC) with ultraviolet lights, which decompose CFC gases into free radicals of chlorine (Cl ), as a catalyst. 

Since the 1970s, it has been known that halogens, in particular the photolysis products Cl and CIO of industrially manufactured CFC gases, have a large impact on stratospheric ozone (Molina and Rowland, 1974), culminating in the discovery of the springtime ozone hole in the lower stratosphere in the Antarctic (Farman et al., 1985). This issue has been thoroughly reviewed by many authors and international research panels. 

Rowland and Molina release CFCs work in the scientific journal, Nature, calculating that continued use of CFC gases at an unaltered rate would critically deplete the ozone layer, http //www.ourplanet.com/imgversn/92/rowland.html... 

Fig. 2.7 The ozone hole over Antarctica in September of 2005 covered an area of more than 24 million square kUometers which is approximately equal to the area of North America. The ozone hole has been forming in the stratosphere over Antarctica since about 1970 as a result of the release of anthropogenic CFC gases into the atmosphere. Computer models now predict that the size of the ozone hole will begin to decline in 2018 and will stop forming altogether in 2068. This is good news because the ozone of the stratosphere absorbs ultraviolet radiation which can cause skin cancer and eye damage in humans and is harmM to marine organisms. The ozone content of the stratosphere over Antarctica has declined annually by about 70% below normal during September and October whereas the decline over the USA has only been between 3% and 6% (Cook-Andersen 2006 Photo courtesy of NASA)...

When CFC gases are released into the atmosphere, they gradually rise into the lower stratosphere because they are not washed out of the troposphere by rain. In the stratosphere the chlorine atoms are released when the CFC molecules are broken up by energetic UV-C radiation as indicated by the reaction ... 

In 1995, three chemists, Mario Molina, Sherman Rowland, and Paul Crutzen, warned world leaders of damage being done to the O3 (ozone) layer. This natural layer of O3 molecules, located from 9 to 30 miles up into the atmosphere, protects the Earth from cancer-causing and damaging ultraviolet radiation from the sun. They discovered that human-made compounds of nitrogen oxides and chlorofluorocarbon (CFC) gases, used as refrigerants and propellants in spray cans, reacted with atmospheric ozone and reduced it. For their work, they received the 1995 Nobel Prize for Chemistry. 

Sherwood Rowland and Mario Molina, alerted the world to the danger of damage being caused to the ozone layer of the atmosphere, about 9-30 miles up, from artificial nitrogen oxides and chlorofluorocarbon (CFC) gases. For this work, the three men were awarded the 1995 Nobel Prize in chemistry. 

One of the chief uses of chloromethane is as a starting material from which sili cone polymers are made Dichloromethane is widely used as a paint stripper Trichloromethane was once used as an inhalation anesthetic but its toxicity caused it to be replaced by safer materials many years ago Tetrachloromethane is the starting mate rial for the preparation of several chlorofluorocarbons (CFCs) at one time widely used as refrigerant gases Most of the world s industrialized nations have agreed to phase out all uses of CFCs because these compounds have been implicated m atmospheric processes that degrade the Earth s ozone layer... 

It is the use of LIDAR devices as tools for spectroscopic measurements on the various gases present in the atmosphere which concerns us here. These include ozone, carbon dioxide, the CFCs (chlorofluorocarbons, such as CFC-11, trichlorofluoromethane, and CFC-12, dichlorodifluoromethane, used as refrigerants) and all those molecules regarded as atmospheric pollutants. 

Chlorofluorocarbons (CFCs). Prior to 1978 most aerosol products contained chlorofluorocarbon propeUants. Since that time, the use of chlorinated fluorocarbons for aerosols has been seriously curtailed. These compounds have been impHcated in the depeletion of the ozone (qv) layer and are considered to be greenhouse gases (see Airpollution Atmospheric modeling). 

The Antarctic ozone hole is the result of anthropogenic release of trace gases into the atmosphere (CFCs in particular), causing a decrease in stratospheric ozone and a subsequent increase in solar ultraviolet radiation reaching the earth s surface. 

Carbon dioxide is not the only gas that can influence terrestrial infrared radiation, and infrared absorption is not the only way that composition influences climate. Other gases that are important for their infrared absorption, sometimes known as "greenhouse gases," include CH4, CCI2F2 (CEC-12), CECI3 (CFC-11), N2O, and O3. Taken together these other species are about of equal importance to CO2. That... 

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