Global warming theory questioned Idea called 'flash in the pan'

September 14, 1993|By New York Times News Service

As the Clinton administration prepares to announce in the next few weeks a plan for controlling waste industrial gases that trap heat in the atmosphere, conservatives and industry groups have mounted a renewed assault on the idea that global warming is a serious and possibly catastrophic threat.

In a drum roll of criticism over the last few months, they have characterized the thesis of global warming as a "flash in the pan," "hysteria," "scare talk" and a ploy by socialists to justify controls on the economy.

The rhetoric is the mirror image of some that was heard five years ago, at the height of the 1988 North American heat wave, when some environmentalists and politicians warned of climatic apocalypse on the basis of assertions by a minority of scientists that global warming was already under way.

The evidence that warming or harm from warming will occur in the foreseeable future is "ludicrously small," argues a 1993 book published by the Cato Institute, a free-market research organization in Washington.

Reining in global warming "will require a degree of bureaucratic control over economic affairs previously unknown in the West," wrote Ben W. Bolch and Robert D. McCallum, professors of economics and chemistry at Rhodes College in Memphis, Tenn., in the book "Apocalypse Not: Science, Economics and Environmentalism."

Dr. Dixy Lee Ray, the former governor of Washington and a former chairwoman of the Atomic Energy Commission, called carbon dioxide "an unlikely candidate for causing any significant worldwide temperature changes" in another 1993 book,

"Environmental Overkill: Whatever Happened to Common Sense?"

In the July issue of Commentary, Jeffrey Salmon, executive director of the George C. Marshall Institute in Washington, said categorically that there is "no solid scientific evidence to support the theory that the earth is warming because of man-made greenhouse gases."

In the midst of this revisionist onslaught, who should the public believe?

Global warming is not a cut and dried issue, and scientific experts are still debating most of its aspects. But few scientists are to be found at either of the extremes that have characterized the political debate.

A substantial number of highly regarded climate researchers have long believed that global warming set off by industrial and automotive emissions is a real possibility that could have serious consequences sooner or later. But they cannot say exactly how severe the effects of the warming will be or when it will come.

And very few climatologists are ready to declare that global warming has begun. Most believe that no clear sign of human-induced change has yet made itself apparent amid the wide natural fluctuations of the earth's climate.

There are two undisputed facts about global warming: first, carbon dioxide, the waste gas produced by burning coal, oil and wood, has been accumulating in the earth's atmosphere over the last century; and second, the gas traps heat that is produced when the sun's energy is absorbed by the earth and then re-radiated.

Given those physical facts, the practical question of interest is how much the earth's climate will heat up after the injection of a given amount of carbon dioxide. Since no experiment can

answer that question, other than the global one now in progress, scientists have turned to their next best method, which is to simulate the earth's climate system in a series of equations that are run on a supercomputer.

This exercise, known as computer modeling, is somewhat controversial because the models are far from perfect and represent a simpler, stripped-down version of the earth's real climate.

After examining results from the best computer models, a scientific advisory committee of the United Nations concluded in 1990, and again in 1992, that a doubling of atmospheric carbon dioxide -- expected to occur by the year 2100 without remedial action -- will raise the average global temperature by 3 degrees to 8 degrees Fahrenheit. In comparison, the earth has warmed by only 5 degrees to 9 degrees since the last ice age.

The U.N. panel and various committees of the National Academy of Sciences, made up of leading experts in the field, have consistently found merit in the global warming theory. Still, the issue is far from settled, with critics questioning the reliability of computer models.

Besides the imperfections of computer models, critics point out an apparent anomaly in the global warming theory: that over the last century the chief rise in global temperature occurred before 1940, though most of the carbon dioxide has been spewed out since then. Defenders say the climate is an erratic system and that a neat, constant relationship between gas input and temperature rise should not be expected.

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