The Heat Is On

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Some experts do not believe the projected cutback is good enough. Says Rowland: "The Montreal agreement simply isn't sufficient to protect the ozone. We should have signed a treaty that reduced CFC production by 95% -- not 50%." Nonetheless, the Environmental Protection Agency has calculated that without the accord, a staggering 131 million additional cases of skin cancer would occur among people born before 2075.

Any similar attempt to ease the greenhouse effect by imposing limits on CO2 and other emissions is unlikely. John Topping, president of the Washington- based Climate Research Institute, argues that adjustments in agricultural production, like limiting the use of nitrogen-based fertilizers, would have only a slight effect. A more important step would be to protect the tropical rain forests, a move that would certainly be resisted by developers. Obviously, the most far-reaching step would be to cut back on the use of fossil fuels, a measure that would be hard to accomplish in industrialized countries without a wholesale turn to energy conservation or alternative forms of power. In developing countries, such reductions might be technologically feasible but would be all but impossible to carry out politically and economically.

Until now, the earth's climate has been a remarkably stable, self- correcting machine, letting in just the right amount and type of solar energy and providing just the right balance of temperature and moisture to sustain life. Alternating cycles of cold and warmth, as well as greater and lesser concentrations of different gases, have forced some species into extinction. The same changes have helped others evolve. The irony is that just as we have begun to decipher the climatic rhythms that have gone on for hundreds of millions of years, we may have begun to change them irrevocably. And as the unforeseen discovery of the ozone hole demonstrates, still more unexpected changes may be on the way.