from one parcel as in the southern hemisphere. (Roan 1989)The end result is that we are losing ozone in both hemispheres. Ozone levels in the atmosphere have been monitored from the ground since the 1950s and by satellite since the 1970s. (Roan 1989) Regional total ozone levels measured from satellites over Antarctica have decreased 30-50% since their monitoring began. (Roan 1989)Since ozone is created and destroyed by solar UV radiation, there is some correlation of ozone concentration with 11-year sunspot cycles. Sunspots emit high levels of electromagnetic radiation. The increased UV radiation contributes to ozone production. Sunspot variations only account for 2 to 4 % of the total variation in ozone concentrations. (Roan 1989) Natural cycles in ozone variation are also associated with the quasi-biennial oscillation in which tropical winds switch from easterly to westerly every 26 months. (Roan 1989) This cyclic change in wind direction accounts for approximately 3 % of the natural variation in ozone concentration.Ozone DepletionFor over 50 years, chlorofluorocarbons (CFCs) were thought of as miracle substances. They are stable, nonflammable, low in toxicity, and inexpensive to produce. Here is a basic view of the chemical formation of a CFC.Over time, CFCs found uses as refrigerants, solvents, foam blowing agents, and in other smaller applications. (Rowland 1989) Other chlorine-containing compounds include methyl chloroform, a solvent, and carbon tetrachloride, an industrial chemical. Halons, extremely effective fire-extinguishing agents, and methyl bromide, an effective produce and soil fumigant, contain bromine. All of these compounds have atmospheric lifetimes long enough to allow them to be transported by winds into the stratosphere. (Rowland 1989) Because they release chlorine or bromine when they break down, they damage the protective ozone layer. In the early 1970s, researchers began to investigate the effects of various che...
