The Heat Is On

Chemical wastes spewed into the air threaten the earth's climate

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Clouds, which shade about half the earth's surface at any given time, are another important climatic factor. Says James Coakley of the National Center for Atmospheric Research: "If you heat up the atmosphere and pump more water in, clouds will change. But how? We don't know." Water vapor, for example, is yet another greenhouse gas, but the white-gray surfaces of clouds reflect solar energy. Which effect predominates? Answer: it depends on the cloud. The bright, low-level stratocumulus clouds reflect 60% of incoming solar rays. But long, thin monsoon clouds let solar heat in while preventing infrared radiation from escaping.

Another contributor to climatic change is the biosphere -- scientific jargon for the realm of all living things on earth. And it is the biosphere that threatens to tip the balance. To be sure, many of its effects are natural and as such have long been part of the climatic equilibrium. Termites, for example, produce enormous amounts of gas as they digest woody vegetation: a single termite mound can emit five liters of methane a minute. The methane escapes into the atmosphere, where it can not only destroy ozone but also act as a greenhouse gas in its own right. "Termites," says Environmental Chemist Patrick Zimmerman, of the National Center for Atmospheric Research, "could be responsible for as much as 50% of the total atmospheric methane budget."

Actually, the biosphere becomes a problem only when humans get involved. In Brazil the Amazon rain forest, which once covered 3 million sq. mi., has been slashed by an estimated 10% to 15% as the region has been developed for mining and agriculture; an additional 20% has been seriously disturbed. When the downed trees are burned or rot, CO2 and other greenhouse gases are released. The same kind of deforestation in Africa, Indonesia and the Philippines, say experts, may already be helping to make the world warmer.

To make matters worse, a host of other gases are now known to add to the greenhouse effect. In 1975, Ramanathan was amazed to discover that Freon, a widely used CFC, was an infrared absorber. "It had a very large impact," he says. "Since then, tracking down the role of other trace gases has become a cottage industry. There are dozens of them, and they are rivaling the effects of increasing CO2." In fact, by the year 2030 the earth will already face the equivalent of a doubling of CO2, thanks to these other rapidly increasing gases, including methane, nitrous oxide and all the CFCs. "These are the little guys," says Schneider. "But they nickel and dime you to the point where they add up to 50% of the problem."

Is there any way to slow either the greenhouse effect or the depletion of the world's ozone? The Montreal accord, agreed to last month after nearly five years of on-and-off negotiations, is a good start on ozone. It calls on most signatory countries to reduce production and consumption of CFCs by 50% by 1999. Developing nations, however, will be allowed to increase their use of the chemicals for a decade so they can catch up in basic technologies like refrigeration. The net effect, insist the treaty's advocates, will be a 35% reduction in total CFCs by the turn of the century.

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