COPING WITH CHANGE

Ever since Rachel Carson's Silent Spring (1962), Americans have been repeatedly alerted to tangible threats-dirty water, polluted air, toxic waste dumps, pesticides-to what is now called "the environment." In recent years, environmentalists, federal officials, and scientists have shifted their attention to "invisible" threats, from airborne asbestos particles in schools to cancer-causing radon gas in the basements of suburban homes. And this autumn, after several summers of drought and record-breaking heat waves, American headline writers rediscovered two unseen phenomena miles above the surface of the Earth: the depletion of the protective ozone layer in the atmosphere and the rise of the "greenhouse effect."

The thinning of the Earth's ozone shield, which screens out harmful ultraviolet light, has been discussed, off and on, since the 1970s. [See box, p. 124.1 The hot 1988 summer and some strong rhetoric have focused far more attention recently on the greenhouse effect, which appears to be gradually making the planet grow warmer.

At an international conference on "The Changing Atmosphere" sponsored by the Canadian government in Toronto last June, some 300 reputable scientists and government officials warned that "Humanity is conducting an uncontrolled, globally pervasive experiment whose ultimate consequences could be second only to a global nuclear war." A "greenhouse doomsday scenario" by author Jeremy Rifkin conjures up images of the Netherlands disappearing under the waves like a latter-day Atlantis, Bangladesh swept by floods claiming millions of lives, and the Mississippi River transformed into a "vast earthen plaidf-while Manhattan's West Side Drive is lined with palm trees.

Exaggerations aside, there is a growing consensus among climatologists and other researchers that both the greenhouse effect and ozone depletion are not simply alarmist fantasies.

Last June, James E. Hansen, a senior physicist at the National Aeronautics and Space Administration (NASA), found himself on the network television news when, noting that the mean global temperature has increased by one degree Fahrenheit during the last century, he told a congressional committee that "the greenhouse effect has been detected and is changing our climate now." On Capitol Hill, Senators Timothy E. Wirth (D.-Colo.) and Robert T. Stafford (R.-Vt.) have each introduced legislation calling for improved energy conservation, more research, and tighter environmental regulation to combat the greenhouse effect.

Scientists are not totally certain that the greenhouse effect is the sole cause of the wanning. The hot summers of the recent past could well be, at least in part, the result of natural climatic fluctuations. "Climate is a complicated thing," notes Roger Revelle of the University of California, "and the changes seen so far may be due to some other cause we don't yet understand." Indeed, even the rising temperatures of the past century were punctuated by an unexplained cool period between 1945 and 1975, when some scientists began to worry about the eventual onset of a new Ice Age. Hubert H. Lamb, a leading British climatologist, is also wary. While the greenhouse effect is real, Lamb believes, the long-term global warming may also have natural causes. Even scientists, he cautions, follow "fashions." A particular theory "catches on and gains a wide following, and while that situation reigns, most [researchers] aim their efforts at following the logic of the theory and its applications, and tend to be oblivious to things that do not quite fit.

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