IDEAS & TRENDS (CONTINUED); A DIRE LONG-RANGE FORECAST By JAMES GLEICK
Published: May 12, 1985
As global nightmares go, the greenhouse effect has managed not to keep policy makers awake nights devising plans of action. Scientists see an assortment of theoretical catastrophes just over the horizon, but the more dire their predictions, the more difficult it seems to find an appropriate response.
A new scientific study has confirmed a swiftly changing view of what causes the greenhouse effect -heightening both the urgency of the problem and the difficulty of controlling it. The study finds that the leading role in the earth's warming belongs not to carbon dioxide, as long believed, but to an assortment of rare, mostly artificial gases, many never seen in the atmosphere before the 1960's.
That supports the view of atmospheric scientists that the world is rushing toward global climate change on a startling scale. Already the changes in the atmosphere are thought to have changed the balance of incoming and outgoing energy, holding in infrared radiation the way the glass of a greenhouse does.
Beginning in a decade or two, scientists expect the warming of the atmosphere to melt the polar icecaps, raising the level of the seas, flooding coastal areas, eroding the shores and sending salt water far into fresh-water estuaries. Storm patterns will change, drying out some areas, swamping others and generally throwing agriculture into turmoil. Federal climate experts have suggested that within a century the greenhouse effect could turn New York City into something with the climate of Daytona Beach, Fla.
But the new view of the greenhouse effect, as much as the old, highlights the difficulty of finding practical weapons against what remains an uncertain demon.
So far, the greenhouse effect has not been clearly felt. In the generations since scientists first theorized that increased carbon dioxide would alter the earth's temperature balance by trapping heat in the atmosphere, no one has been able to measure a significant warming. Scientists have explanations for that, and they believe their temperature curves will soon soar off the scale. But for now the greenhouse effect remains part of a hypothetical, if not so distant, future.
Even if officials were moved by the urgency of the problem, it would be hard to know what they should do. The Environmental Protection Agency estimated last year, for example, that a drastic 300 percent worldwide tax on fossil fuels to discourage their use - a tax conceivable in a world of scientists, if not in a world of politicians and business executives - might make a tiny difference of about five years.
So the Government waits. ''It's a creeping problem, an incremental problem, and we're very bad at dealing with incremental problems,'' says Stephen H. Schneider, a climate expert at the National Center for Atmospheric Research. ''There always seems to be an intermediate problem of higher value.''
Until recently, the culprit seemed to be strictly carbon dioxide, which has been increasing steadily for the last century. But the new study, to be published next month in the Journal of Geophysical Research, confirms that an even greater greenhouse effect is likely to come from 30 or more trace gases, mostly emitted by industry and agriculture. These gases are more efficient at trapping heat on its way out to space, and they are increasing much faster than carbon dioxide.
That seriously complicates the problem of finding effective controls. And it suggests to climate experts that they should be giving more credence to the high end of the most recent predictions. But those predictions have great uncertainty built in. ''Whenever you work with a climate model, you are trying to play God,'' says V. Ramanathan, one of the authors of the new study. For example, as the bright polar icecaps melt, they might reflect significantly less sunlight back out to space - and since the earth would then absorb that much more energy, the warming would be amplified. For similar reasons, big changes in temperature could come from small changes in cloud patterns, and scientists aren't sure whether the changes will warm or cool.
In an October 1983 report, the Environmental Protection Agency estimated that the sea level could rise as much as 11 feet by the end of the next century - or as little as 2 feet. It settled on 5 to 7 feet as the likely range. The higher figure would put substantial pieces of Florida and Louisiana under the waves and flood parts of some coastal cities. Even the lower figure would cut away chunks of shoreline. Experts estimate that a one-foot rise in the ocean could erode 100 to 1,000 feet of sand beach all along the Atlantic and Gulf Coasts.
One certainty is that people will first feel the greenhouse effect not in slight changes but in extremes. Areas that now get severe floods once a century might get them once a decade. Temperate locales will get many more heat waves and many fewer cold snaps. In the long run, to be sure, not all the news would be bad. Plenty of places could benefit from extra warmth, and if the corn belt loses territory to the south it could gain it to the north. But in the century to come scientists expect painful dislocations. Some argue that the Government ought to be aggressive about acting, even in small ways, to buy time. One way or another, a lesson is under way in people's ability inadvertently to change the face of the planet.
''The only way to be certain is to perform the experiment on ourselves,'' says Mr. Schneider. ''For better or worse, that's what we're doing.''