By the early 1980's, the thin O3 layer over Antarctica was showing significant depletion, based on measurements by a British team of scientists working there. The antarctic measurements, made public in 1985, soon lead to NASA's discovery that the Nimbus satellites had been detecting the same ozone losses for years, but the data was not being interpreted properly. Computer programs were soon revised, and full-color images documenting the formation of the now famous "ozone hole" appeared.
In August and September of 1987, NASA high-altitude aircraft flying through the hole verified conclusively that chlorine monoxide, ClO, is present in large concentrations where the O3 has been depleted.[Ozone Crisis, Roan,Wiley Science,1989] This was final "iron-clad" proof that CFCs were the culprit. Although a top chemist from DuPont (largest producer of CFCs) witnessed the NASA tests first-hand, it was not until nearly 6 months later that DuPont's president, under mounting public pressure, announced that the company would eventually cease production of CFCs. No cutoff date was promised.
The size of the hole varies each year. In October 1985 the size was greater than the area of the continental US. The hole forms austral spring in Antarctica, during August or September, and peaks in size, usually in October. In 1987 the hole size hit record levels - larger than the entire Antarctic continent. While size fluctuates from year to year, depending on weather, the 1989 hole was equal in size to the record setting 1987 hole. Ozone decreases of approximately 50% are measured inside the hole. Some NASA researchers are predicting the hole will increase significantly after 1991, speculating that the current high sunspot activity may be partially compensating for ozone losses. After 1991, the 11 year sunspot cycle begins its decline, producing lower natural levels of O3 in the upper atmosphere. Fewer sunspots are known to generate less UV radiation, which creates ozone from ordinary oxygen.
In recent years a smaller ozone hole has been observed near the north pole as well. The CFC chlorine seems to react vigorously with ozone at very cold temperatures, in the presence of thin, icy clouds over polar areas. NASA has also measured ozone losses of about 5% in the winter and yearly averages of a 3% O3 decrease over the northern United States.
High altitude ozone loss causes health problems, as UV levels of sunlight become increasingly more powerful. EPA studies predict an extra 20,000 cases of skin cancer for each percentage point drop in O3 level. Sharon Roan, in her book, 'Ozone Crisis' reports that cases of malignant melanoma, the potentially deadly form of the disease, have increased 93% in the last 8 years. Eye cataracts and other vision-related disorders are also projected to increase.
Research is beginning to reveal that high UV levels on our ozone-depleted planet will result in lowering the productivity of plankton in the oceans. Plankton are at the bottom of the marine food chain, so less plankton may soon mean smaller catches for the world's commercial fishing industry. Yields for crops, such as corn, wheat, and soybeans, are also projected to drop as UV radiation increases. ***
