k between ozone destruction and man made halocarbons exists, other factors also influence ozone concentrations:
Stratospheric sulfate aerosols - Large explosive volcanoes are able to place a significant amount of aerosols into the lower atmosphere, as well as some chlorine. The effects of a large volcanic eruption on total global ozone are calculated at less than 3%, with effects extending no more than 2 to 3 years (Ozone home..., 1996).
Stratospheric winds - Every 26 months the tropical winds in the lower stratosphere change from easterly to westerly and then back again, an event called the Quasi biennial Oscillation (QBO). The QBO causes ozone values at a particular latitude to expand and contract roughly 3% (Ozone home..., 1996).
Greenhouse gases - The existence of greenhouse gases has prompted the possibility of changing weather patterns. This has lead to computer modeling that predicts cooler stratospheric temperatures, leading to more polar stratospheric clouds and more active chlorine in the area of the Antarctic ozone hole (Ozone home..., 1996).
Sunspot cycle - Ozone is created by solar UV radiation. the amount of UV radiation produced by the sun is not constant but varies by several percent over an 11 year cycle. Comparisons of yearly ozone concentrations show a small 111 year variation in global ozone of about 2%. Episodes of unusual solar activity, solar storms and large solar flares, would certainly alter this value (Ozone home..., 1996).
Stratospheric chlorine - The release of man made halocarbons. Careful subtraction of other natural factors yields a net decrease of 3% per decade in global ozone from 1978 through 1991. This is most certainly due to catalytic degradation by stratospheric chlorine (Ozone home..., 1996).
Halocarbons, CFMs and Stratospheric Chlorine
In 1973, Richard Stolarski and Ralph Cicerone, two scientists from the University of Michigan, were exploring the possible side effect...