In the mid 1970′s there was considerable discussion about the thinning of the ozone layer in our stratosphere and about the harmful effects that the thinning layer would create. It was a major cause for concern.
It was known that the ozone in the stratosphere, the altitude where jet airplanes fly, helps to filter out much of the very harmful ultraviolet rays from the sun. Many feared that if the ozone layer continued to decrease and become thinner that the incidence of skin cancer would increase disastrously. It was also feared that the increase in ultraviolet radiation would adversely affect food crops around the world and would destroy the phytoplankton in the oceans, the important base of the marine food chain.
The normal, healthy ozone layer blocks about 90-99 percent of the harmful ultraviolet-B, or UV-B, radiation from reaching the ground. Other types of ultraviolet rays routinely penetrate the ozone layer, but, luckily, those rays are not harmful to us.
Two scientists, Sherwood Rowland and Mario Molina, working at the University of California, Irvine, theorized that the release of chlorofluorocarbons (CFCs) into our atmosphere could cause the destruction of ozone through a simple chemical reaction. In 1974 they published an article in the magazine, Nature, which caused a sensational public stir. A federal investigation was initiated and their research was validated in 1976. Two years later the Environmental Protection Agency and the Consumer Safety Commission issued a ban against the use of CFCs in aerosol cans. It didn’t take long for companies to find alternative, environmentally safe alternatives to use as propellants in aerosol cans. The use of CFCs as cooling agents in refrigeration units and the use of CFCs in cleaning solvents were also discontinued.
Meanwhile, British scientists working in Antarctica between 1975 and 1985 observed a hole in the ozone layer opening overhead. They reported their research about the ozone hole in the May, 1985, edition of Nature magazine. Although a thinning of the ozone layer over the Antarctica continent is normal each winter, due to the decreased temperatures and the constant wind patterns, the British scientists reported that the ozone layer was becoming a hole and was not repairing itself during the spring and summer when temperatures warm.
This observed change, the new “ozone hole,” caused enough alarm that the United Nations convened an international conference in Montreal. The resulting discussions produced the Montreal Protocol of 1987. The Protocol called for the phaseout of CFCs, halons, carbon tetrachloride, and methyl chloroform in all nonessential commercial uses by the year 2000.
Not surprisingly, the rapid adoption of the Montreal Protocol has resulted in the most significant global environmental reversal in history. Since there are now few CFCs and other ozone depleting chemicals being released into the atmosphere, the ozone hole will begin to heal itself naturally over time.
The concentration of CFCs in the atmosphere reached its peak in about 1995, and the ozone hole over Antarctica has stabilized and has begun to decrease. The ozone hole has grown to about the size of the North American continent. Since the chemicals have a normal life expectancy in the atmosphere of 40 to 100 years, scientists now estimate that a complete, natural repair of the ozone layer will be reached by about 2070.
It is to the credit of scientists and politicians worldwide that the potential disastrous harm of the total destruction of the ozone layer was quickly recognized and that fast action was initiated to stop the activities that had caused the ozone depletion. As a result of worldwide cooperative effort the ozone problem is no longer growing worse and 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 before they become unmanageable.