Stratospheric Ozone Depletion
Ozone, O3, is a chemical hybrid in which a central oxygen atom forms a single covalent bond, and a double covalent bond with two other oxygen atoms . It has a “normal” concentration in the atmosphere of 0.3 parts per million by volume. In the so-called “ozone hole”, however, its concentration falls below 50% of that norm . This hole, which appears over the Antarctic in September of every year, has been observed since the late 1970s. Since 1985, when scientists discovered it had grown to massive size, the problem of ozone depletion has been the focus of a great deal of attention and some efforts has been made to cope with it. At this writing the problem cannot be considered as having been solved. The massive Antarctic hole grows larger with passing years (it is now, intermittently, nearly the size of North America), and ozone depletion outside this region is going on throughout the globe.
The culprit is thought to be chlrofluorocarbons (CFCs), compounds of chlorine, flourine, and carbon. These substances have an extremely stable molecular structure and have been widely used since the 1920s as refrigerants, spray can propellants, and cleaning agents. Because of their great stability they tend to accumulate in the atmosphere. Under certain climatological conditions they break down atmospheric ozone. This skews the natural equilibirium between spontaneous break down and reformation of that molecule and thus diminishes its concentration.
This lowering of ozone concentration has a whole set of deleterious effects. For ozone shields the surface of the earth from short wave length, high-energy, ultraviolet radiation coming from the sun. Ozone depletion therefore means a higher chance of sunburn, skin cancer, cataracts, birth defects, and crop reductions .
Efforts to cope with the problem have not been lacking. The Montreal Protocol of 1987, as reinforced by the London Amendment of 1990 and the Copenhagen Amendment of 1992, has done a great deal to reduce the emission of new CFCs into the atmosphere by banning their manufacture and use . In 1995 there was some evidence that ozone concentration was increasing, but the jury is still very much out on the question of whether or not the agreements currently in place will produce the desired effect.
The above paragraphs give a brief sketch of the nature of the ozone problem, its cause, and its possible solution. In what remains I would like to give my assessment of what the fact of ozone depletion means with respect to humanity’s relationship with the environment.