But scientists have been seeing hints all year. In April the U.S. Environmental Protection Agency announced that the ozone layer is now 5 percent thinner over the Northern Hemisphere in winter and early spring than it was a decade before. That portends more cases of UV-induced cataracts and skin cancer-an extra 12 million cancer cases among Americans over the next 50 years. Already, skin-cancer rates have doubled since 1980. Even more dispiriting, the ozone is slipping away despite the best-intentioned steps to save it. By next year, for instance, the United States will halve its production of chlorofluorocarbons (CFCs), the chemicals primarily responsible for ozone loss, from 1986 levels. By 1997, Du Pont, the world’s largest CFC maker, will stop producing these refrigerants and foam blowers, the company announced last week; several major German firms will beat that by two years. And EPA Administrator William Reilly told NEWSWEEK that his agency persuaded China, which had been planning to build 300 million CFC-cooled refrigerators, to use substitute coolants instead. All this will help, but not as much as once hoped. Robert Watson of NASA calculates that the ozone layer will still thin at least another 3 percent in the 1990s. And even if CFCs were banned tomorrow, so many tons of the gases are on the way to the stratosphere that it would take until the middle of the next century for the ozone layer to recover.
Can anything be done? Reilly is calling for “a reconsideration of all efforts underway to respond to” ozone depletion. That means banning CFCs before the millennium, as the 93 nations will consider when they meet in Copenhagen next August. It means, too, tackling other ozone eaters, such as halons. These gases can extinguish fires in a split second. Halon systems were standard equipment in tanks on both sides during the gulf war. They are also ubiquitous around expensive computer installations, a use for which there are no good substitutes yet. Another voracious ozone eater is methyl bromide, a crop fumigant. Controlling its use, says Susan Solomon of the National Oceanic and Atmospheric Administration, would have a “rapid and large influence on the ozone layer.”
But there may be a downside to fixing the ozone problem. New data suggest that, even though CFCs warm the planet, ozone depletion cools it. That’s because when ozone absorbs UV rays the stratosphere warms (diagram). Less ozone, therefore, means a cooler stratosphere and a cooler planet. So if nations manage to patch the ozone, the world may well heat up, exacerbating the greenhouse effect that threatens to cause sea levels to rise, ferocious storms, droughts and heat waves. In fact, if not for ozone loss, the greenhouse effect might have been more pronounced by now. That finding may settle an ongoing, and frequently nasty, greenhouse debate. Given how much carbon dioxide and other heat-trapping gases have been belched out of power plants and cars in the last 100 years, the Earth should be warmer than it is; since it’s not, argue skeptics, the greenhouse theory must be wrong. The ozone effect may explain why the Earth is only slightly warmer than the historical norm despite the buildup of greenhouse gases.
The United States is counting on stemming the greenhouse effect by eliminating CFCs. But if doing so will simultaneously fatten the ozone layer, and thus cause warming, we need other solutions. UNEP’s Mostafa Tolba said last week that the target must be carbon dioxide (CO2), the chief heat-trapping gas. But the United States argues that controls on CO2–Switching to nonfossil fuels, requiring higher-mileage cars and energy-efficient factories, for instance–will prove too costly. The Bush White House has expressed little interest in CO2 limits. Humans have turned the atmosphere into a giant chemistry experiment, and we have precious little idea how to control it.
There are two crises in the skies: the thinning ozone layer and the steady accumulation of greenhouse gases. It now appears that they’re related. MORE CFCs
1 CFCS, chemicals used as coolants and fire extinguishers, destroy ozone in the stratosphere.
2 A thinner ozone layer absorbs less UV radiation than a thicker layer. The less UV absorbed, the cooler the stratosphere.
3 But the increased UV from a thinner ozone layer is harmful. Result: more skin cancer and, possibly, damage to crops and marine life. LESS CFCs
1 If CFCs are curtailed, the ozone layer will eventually repair itself. Result: more UV absorbed in the stratosphere.
2 The less UV reaching the planet’s surface, the fewer cases of skin cancer and cataracts.
3 But a thicker ozone layer, absorbing more UV, will be warmer. It will radiate more heat toward Earth, worsening the greenhouse effect.
