Montreal Protocol

THE MONTREAL PROTOCOL is an international treaty designed to protect the ozone layer by phasing out the production of a number substance (such as CFCs—Chlorofluoro compounds) believed to be responsible for ozone depletion. In the late 1920s, chemicals called chloroflourocarbons (cloro-floro-carbons) or CFCs, were invented. These chemicals were not poisonous and did not harm fabrics, plants, or people. Companies thought they were great products and used them in refrigerators, air conditioners, styrofoam packaging, and spray cans. From the 1920s to the 1970s, billions of CFC molecules were released into the air.

In the 1970s, scientists began to wonder what happened to all the CFCs after they had been in the air for a while. Scientists eventually learned that CFCs could float past the troposphere (troposphere is a layer of atmosphere that is closest to the Earth. It extends to about 3.7–10.5 mi. (6–17 km.) above the Earths surface and is thickest at the equator. Temperatures in the troposphere decrease as altitude increases. They are warmer nearest the Earth, in part because gases in the troposphere are warmed by heat radiated from the earth.) up into the stratosphere (stratosphere is the second layer of atmosphere, and extends out beyond the troposphere, to about 31 mi. (50 km.) above the earth. Gases in the stratosphere are heated mainly by incoming radiation from the Sun; temperature in the stratosphere gradually increases as altitude increases. As a consequence of temperature differences between the troposphere and stratosphere, and the resulting circulation patterns, exchange of air between the two layers is slow. The stratosphere is also known as the ozone layer. The distribution of ozone is closely linked to the vertical structure of the atmosphere. Approximately 90 percent of all ozone molecules are found in a broad band within the stratosphere. This layer of [Page 672]ozone-rich air acts as an invisible filter to protect all life forms from over-exposure to the Suns harmful ultraviolet (UV) rays. Long-term ozone depletion is result of human-activity.) where UV rays would break them down. The chemicals that make up CFCs, mainly chlorine and fluorine, float around the stratosphere, breaking up ozone molecules.

Although CFCs were invented in 1920s, and research in the impact of CFCs on the ozone layer began as early as the 1930s, it received attention mainly in 1970s. During the 1970s, concerns arose that stratospheric transport aircraft might damage the ozone layer. This concern started in 1973, when the American Chemists (Frank Sherwood and Mario Molina) decide to study the impact of CFCs on the Earths atmosphere. They discovered that CFC molecules were stable enough to remain in the atmosphere until they got into the stratosphere where they would finally be broken down by ultraviolet radiation releasing a chlorine atom, after an average of 50–100 years for the two common CFCs.

In 1974, Sherwood Rowland and Mario Molina discovered a dramatic change in the chemical composition of our atmosphere, an enormous increase in concentration of chlorine throughout the world. This increase in chlorine is attributed to widespread use of CFCs. It was at this time that the theory was proposed that CFCs were depleting the ozone layer. At the time, CFCs were used in refrigeration, aerosol cans, and some industrial processes. Initially greeted with a great deal of skepticism, further research and monitoring began to convince the scientific community that the CFC hypothesis might be valid. In the late 1970s and early 1980s, some national governments imposed bans on CFCs as aerosol and other propel-lants in non-essential uses for antiperspirants, hair-sprays, and deodorants. In 1977, the United Nations Environment Program (UNEP) established the Coordinating Committee on the Ozone Layer.

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