In the early 1970’s, a pair of scientists working at the University of California, Irvine, theorized that chlorofluorocarbons (CFCs) could be responsible for depleting large numbers of ozone molecules in our atmosphere. The implication of this theory was that the destruction of the protective ozone layer would allow the sun’s harmful ultraviolet rays to penetrate in such concentration as to cause tremendous damage to life on earth.

The healthy ozone layer normally blocks 90-99 percent of the ultraviolet-B, or UV-B, radiation from reaching earth. Other types of ultraviolet light penetrate the ozone layer, but they are not harmful to us. The UV-B rays can cause skin cancer and cataracts in people, harm plant life, and degrade certain manmade and natural materials. In the southern oceans the UV-B radiation is harmful to phytoplankton, which is the abundant base for the entire ocean food chain.

Sherwood Rowland and Mario Molina understood the importance of their theory and published an article in the popular scientific magazine, Nature, in 1974. Their report caused a sensational stir and a federal investigation was initiated. Their findings were validated in 1976, and by 1978 the United States Environmental Protection Agency (EPA) issued a ban against the nonessential aerosol cans, the use of which released large amounts of CFCs into the atmosphere. Companies were quickly able to find alternative propellants that contained no chemicals harmful to the ozone layer. CFCs were also discontinued for use as cooling agents in refrigeration units and for use in cleaning solvents.

From 1975 to 1985 British scientists stationed in Antarctica recorded decreasing concentrations of ozone over Antarctica. They identified a hole in the ozone layer and reported it in Nature magazine in May, 1985. The reason that the depletion of the ozone is more prevalent over Antarctica than anywhere else is because the colder winter temperatures and regular wind patterns over the continent cause a natural shrinkage of the amount of ozone. Normally, as spring temperatures warm the atmosphere, the ozone returns to normal amounts. However, the scientists recorded that the ozone layer was decreasing, causing a larger and larger hole to open each winter.

As a result of this startling new finding the United Nations convened an international conference that resulted in the Montreal Protocol of 1987. The Protocol, ratified in 1989, called for the phase out by 2000 of CFCs, halons, carbon tetrachloride, and methyl chloroform.

The quick adoption of this cooperative measure worldwide has resulted in the most important environmental reversal in history. With few CFCs and other harmful chemicals being released into the atmosphere, the ozone will be able to naturally replenish itself in time.

The reason that the damage will take a long time to repair is due to the extent of the damage and to the long life of the chemicals already in the atmosphere. The hole over Antarctica has grown steadily since the international actions initiated in 1987. The ozone hole has grown to about the size of the North American continent, but after 20 years of chemical controls, the hole is no longer growing in size. The controlled chemicals will last for 40 to 100 years in the atmosphere, so scientists now estimate that a full recovery of the ozone layer will be reached by about 2070.

The enormous potential harm posed by the prospect of the total destruction of the ozone layer was quickly recognized internationally and resulted in fast action being taken to cease activities that were causing ozone depletion. The outcome of the cooperative effort is the good news that the problem is no longer getting worse and that the ozone layer will eventually recover.

The hope for the future is that international cooperation will be able to identify, control, and reverse other environmental problems as they occur!