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Good news for greenhouse worriers.

Good news for greenhouse worriers

In the 1970s, consumers in the United States and other countries unwittingly took a major step toward reducing the threat of future global warming.

Fear of another environmental catastrophe -- a vanishing ozone layer -- drove many people to stop using aerosol spray cans containing chlorofluorocarbons (CFCs). Yet aside from harming ozone, CFCs acts as "greenhouse gases" that warm the Earth by absorbing infrared radiation. If consumers had continued to spray with abandon, CFCs would have surpassed carbon dioxide by now in terms of current human contributions to the greenhouse effect, according to James Hansen, Andrew Lacis and Michael Prather at NASA's Goddard Institute for Space Studies in New York City.

In the Nov. 20 JOURNAL OF GEOPHYSICAL RESEARCH, the NASA scientists report that CFCs now constitute 25 percent of the annual human additions to the greenhouse effect. Reflecting industrial emissions and the continued sale of CFC-containing aerosol sprays in many countries, this percentage represents an increase over the past -- but without the 1970s cutbacks, it would have been much greater, Hansen says. In comparison, carbon dioxide today accounts for 57 percent, methane for 12 percent and nitrous oxide for 6 percent.

Many policy experts believe it will be easier to eliminate CFCs than to drastically cut emissions of carbon dioxide, and most countries are currently reducing their use of CFCs as part of an international agreement (SN 6/10/89, p.367). "We can make an enormous contribution toward decreasing the current contributions by phasing out the CFC part," Hansen says. He warns, however, that while proposed substitute chemicals should not harm the ozone layer as much as CFCs do, several of them would contribute to the greenhouse effect.

Hansen says the NASA study shows that moderate CFC decreases that slow an exponential increase in emissions can make a big difference after a while. "This is an example which I think provides some optimism about the possibility of influencing what's going to happen," he says.
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Publication:Science News
Date:Dec 2, 1989
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