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Ahead in the Clouds

Susan Solomon helped patch the ozone hole. Now, as a leader of a major United Nations report—out this month—she's going after global warming

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"It was radical," says Mack McFarland, a chemical physicist at DuPont Corporation who previously worked with Solomon at NOAA. "She was suggesting a completely new area of chemistry for the atmosphere—that there could be reactions not just between molecules but on molecules in the ozone layer and at incredibly low temperatures. Other people had a hard time accepting that."

Yet it was viewed as an idea worth testing, and Solomon was put in charge of the 1986 expedition, which was organized by NOAA and NASA. En route to Antarctica, a reporter in New Zealand asked her what it was like to be the only woman among so many men. "Gosh," she quipped. "They are all men, aren't they?"

In their three months at McMurdo, Solomon and her team worked out of a small wooden cabin outfitted with computers and a visible light spectrometer, an instrument the size of a portable sewing machine. The scientists analyzed light for wavelengths that indicate the presence of ozone, chlorine dioxide and other ozone-depleting chemicals. They took turns standing on the cabin roof and directing moonlight through a tube and into the spectrometer. It was so cold, dipping to minus 40 degrees, that one night Solomon's right eyelid froze shut. Not a problem. "I'm a theoretician," says Solomon. "I'd never collected any data for any experiment before, and I just loved it."

Solomon and her colleagues not only confirmed that the ozone hole was real, but they also showed that it was being caused by chemical reactions between CFCs and the polar stratospheric clouds, just as Solomon had predicted. "Scientists were surprised but relieved," McFarland recalls. "We knew the cause and could do something about it."

Only a year after Solomon's research was published, governments started to act. Representatives from 24 nations met in Montreal in 1987 and signed a treaty to limit the use of CFCs. (The United States and other countries had already banned CFCs as propellants in aerosol cans, based on the early studies of their potential for harming the atmosphere, but the chemicals were still being used in refrigerators, air conditioners and cleaning solvents.) Today, more than 180 countries, including the United States, have signed the "Montreal Protocol on Substances that Deplete the Ozone Layer" as well as amendments calling for a complete ban on CFCs. In 2000, President Cinton awarded Solomon the National Medal of Science for her ozone hole research; the citation praised her "for exemplary service to worldwide public policy decisions and to the American public." She was one of the youngest members to be elected to the National Academy of Sciences, the country's most elite scientific organization.

The earth's ozone layer has stabilized in the past ten years, and although CFCs from old refrigerators are still floating up into the atmosphere, almost no new ones are being produced. Climate scientists predict that the ozone hole over Antarctica will disappear by the end of this century and the ozone layer over the rest of the planet will thicken back up. "With luck, I'll live long enough to see the layer close to being fully restored," Solomon says.

Part of that environmental success can be credited to the company that manufactured most of the world's CFCs, DuPont. It announced in 1988 that it would voluntarily stop CFCs production, and company chemists soon devised replacement chemicals for air conditioners and refrigerators.

Solomon knows the current climate crisis won't be as easy to solve as the ozone problem. (The ozone hole does not contribute noticeably to global warming.) For one thing, the health dangers of global warming, such as a possible increased range for malaria and other tropical diseases caused by warm-weather microbes, may not be immediate or dramatic. And there's no simple alternative to the burning of fossil fuels. But she's hopeful that the science presented in this month's report will inform public attitudes about global warming. "I don't think people realize how much solid data scientists have or what the data mean," she says, referring to the dramatic increase in global temperatures in the past few decades. "I'm an optimist," she adds with a smile. "I really do believe that we and our governments will do the right thing."

Virginia Morell is the author of Ancestral Passions and Blue Nile, and a co-author of Wildlife Wars.

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