SI Vault
Robert H. Boyle
November 16, 1987
Man-made pollutants are producing changes in the earth's climate that may prove catastrophic
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November 16, 1987

Forecast For Disaster

Man-made pollutants are producing changes in the earth's climate that may prove catastrophic

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But the publication of the Rowland-Molina report was just the beginning of the battle against CFCs. The Governing Council of the United Nations Environment Programme convened a panel of experts to examine the problem in 1977. The following year, Canada, Sweden and the U.S. banned the use of CFCs in aerosol sprays (but only a few other countries have followed suit and CFCs from aerosol sprays still account for about 15% of the global total according to the Environmental Defense Fund). In March 1985, after eight years of continued UN-sponsored meetings, the U.S. and 20 other countries signed what is now known as the Vienna Convention for the Protection of the Ozone Layer. The convention called for international cooperation in research and monitoring. It also provided for the adoption of international protocols to limit the emission of ozone-depleting substances, should such measures be necessary. Richard Benedick, a career diplomat who was the American deputy assistant secretary of state for environment health and natural resources, signed the document for the U.S., calling it "a landmark event. It was the first time that the international community acted in concert on an environmental issue before there was substantial damage to the environment and health."

Two months later, in May 1985, Nature published alarming new information about CFCs. This paper was written by Dr. Joe Farman, an atmospheric scientist with the British Antarctic Survey, which had been routinely measuring the ozone layer above the Antarctic since 1957. He and others examined the data and saw that in recent years the ozone levels in September and October (the Antarctic spring) had fallen considerably.

The British measurements came from ground-based observations, and the wary Farman wondered if NASA satellites had recorded the phenomenon from space. At first it appeared that they had not. However, further checks of NASA computer data revealed that the hole in the ozone layer was apparent as early as October 1978—the first year in which such satellite comparisons could be made—and had reappeared each year at roughly the same time. The Farman paper suggested that the ozone drop might be tied to CFCs. But other scientists thought the unique weather dynamics above Antarctica were a more important factor. In August 1986, Dr. Susan Solomon, an atmospheric chemist with the National Oceanic and Atmospheric Administration, led a team of scientists to the Antarctic to study the hole. At its maximum, it was the size of the U.S. The scientists also noticed that some ozone depletion extended as far north as Tierra del Fuego and Patagonia. This past August four more teams traveled to Antarctica to make further observations. Although scientists are still going over their data, there now seems to be general agreement that the ozone hole is caused primarily by chlorine from CFCs.

Depletion of the ozone layer increases the amount of ultraviolet radiation reaching the earth, and the potential effects on human health are considerable. First, there's skin cancer. It is the most common form of cancer in this country, with an estimated 500,000 cases discovered each year. A study published by the Environmental Defense Fund projects that by 2025 there will be an additional 1.4 million incidences of skin cancer over the present rate if nothing is done to control ozone depletion.

Cataracts are another threat posed by elevated UV levels. So is alteration of the immune system. Research on the effects of UV radiation on the immune system has been done using mice as subjects. According to congressional testimony by Dr. Margaret L. Kripke, chairman of the department of immunology at the University of Texas, "There is considerable evidence that the UV rays damage a type of immune cell found in the skin, the Langerhans cell, and that this damage leads to activation of suppressor lymphocytes, instead of the appropriate immune response. Thus, although the initial damage is localized to the area of skin exposed to the UV radiation, the resulting immunological suppression is systemic, because the suppressor cells circulate throughout the body."

Not only mankind is at risk. Experiments with marine organisms have shown that UV radiation can damage animals in the marine food chain. The potential for damage to vegetation is also high. Dr. Alan Teramura, a professor of physiological ecology at the University of Maryland, reports that although some plants may adapt to UV radiation, many are adversely affected by increased levels. In tests, higher levels of UV radiation caused plant stunting, reduction in leaf area and reduced physiological vigor—the latter rendering them more vulnerable to pests and disease. In a six-year study of soybeans, UV radiation was increased to simulate a 25% reduction in the ozone layer; the result was a 20 to 25% loss in yields.

"Unlike drought or other geographically restricted stresses, increases in UV would affect all areas of the world simultaneously," Teramura says. "Even small reductions in crop yield on a global basis could lead to considerable economic consequences." Almost all knowledge of the effects of UV on plants comes from studies of cultivated crops, but these account for less than 10% of the world's vegetation. We have little or no information on the effects on the other 90%—the forests, grasslands and shrub lands. In fact, there is much we don't now know about the extent of the damage that may be done by CFCs rising into the sky, because nothing like it has ever happened before. But when it comes to massive changes in climate, there are some precedents that may give us signs of what to expect.

Over the last 2,000 years, the earth has undergone two major changes in climate. The first was a warm period known to scientists as the medieval warm epoch; it occurred between the years 800 and 1250, when average global temperatures were about the same as they are now. Certain areas, however, were distinctly warmer. During that time barley and oats were grown in Iceland and vineyards flourished in England, where sea levels were gradually rising. In Belgium the rising sea made Bruges, now some 15 miles inland, a seaport.

Around 985, the Vikings began to colonize Greenland, which had been discovered by Eric the Red. But by the end of the 13th century Arctic sea ice had spread through Greenland's waters and had become such a navigational hazard that the colonies died out.

The medieval warm epoch was soon followed by the Little Ice Age, which lasted from about 1550 to 1850, during which the global climate was generally about 1�C (2�F) cooler than now. In India, the monsoons often failed to arrive, prompting the abandonment in 1588 of the great city of Fatehpur Sikri because of lack of water. The Thames froze over several times in the late 1500s. Year-round snow, now absent, covered the high mountains of Ethiopia. The vineyards of northern France died off.

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