Global warming? There's no consensus yet

April 08, 1997|By Linda Seebach

PLEASANTON, Calif. -- Is human activity warming the earth? If you assume scientists long ago answered that question with a definite yes, you'd have been surprised by the lively debate on causes of climate change at the December meeting of the American Geophysical Union, held at San Francisco's Moscone Center.

Hugh Ellsaesser, who retired from the Atmospheric Science Division of Lawrence Livermore National Laboratory in 1986, distributed his paper, ''Has a Man-Induced Climate Change Been Identified in the Temperature Record?'' His answer is ''a confident no.''

Politicians seeking justification for sweeping policy changes cite the scientific evidence, Dr. Ellsaesser says, but the papers they refer to generally don't make the claims that the politicians attribute to them.

A statement inserted at the last minute in the 1995 United Nations report of the Intergovernmental Panel on Climate Change says, ''The balance of evidence suggests that there is a discernible human influence on global climate.''

That statement, Dr. Ellsaesser believes, ''was studiously crafted to induce the media to broadcast to the citizens and policy makers of the world a message which few if any of the researchers, on whose work it was based, are yet willing to defend before the scientific community.''

Before the geophysical conference, climatologist Pat Michaels of the University of Virginia read the summaries of the papers being presented and tallied them in his breezy and irreverent bi-weekly World Climate Report.

Of the 22 papers on the schedule, he wrote, 11 appeared to be generally supportive of the international panel's assertion about human impact on the climate. Eight of the papers seemed to argue that the worries about climate change were overblown, or that it would be too small to justify much political meddling, and three Mr. Michaels couldn't classify.

''Seems like the scientific community is at odds with itself over this issue!'' he said.

And that's true, because this is very difficult science. The ''fingerprint'' of human influence on climate, if it exists, is just at the edge of detectability, almost lost in the noise of natural

variability. The earth's climate has been both much colder and much warmer during its history, long before humans existed to influence it. Even within recent times, there was a warm period jTC during which the Vikings colonized Greenland, and succeeding cold centuries called the Little Ice Age when those colonies perished. Nobody knows why.

Fastest computers

Large-scale observations of the upper atmosphere have only become available within the last 15 years or so, and the fastest computers aren't fast enough to model all the intricacies of global climate, even if everybody agreed on how to do it. So it's true, as alarmists cry, that some computer models predict substantial warming of the earth due to ''greenhouse gases'' such as carbon dioxide. What's not known is whether the models are any good.

In in the magazine Science, Simon F. B. Tett and his co-authors reported last fall that computer simulations of climate are gradually coming to agree better with observations. The best simulations take account of greenhouse gas, sulfate aerosols in the lower atmosphere and ozone in the stratosphere. But since greenhouse gases tend to warm the climate, aerosols tend to cool it, and ozone can do either or both, depending on whether it's low or high in the atmosphere, there is plenty of uncertainty.

''The uncertainties remaining,'' the authors say, ''are due to imperfect knowledge of radiative forcing, natural climate variability and errors in observations and model response.''

All the simulations, the paper acknowledges, predict a particular pattern of warming in the tropics ''which is not seen in the spatially averaged observations and may therefore be due to model error.''

In lay terms, that means none of the models describes the present state of the earth accurately. So why would anyone want to rely on their predictions of the earth's future?

Politicians would, because it's their excuse to expand government control over people's lives. The United States is perilously close to committing itself, by treaty, to vast dislocations of its economy to counter a threat that may not exist.

Vice President Gore, back when he was still rooted in the Senate, wrote a book called ''Earth in the Balance,'' which uncritically accepted every apocalyptic model anyone had dreamed up (most of them no longer believable). He called for a ''Strategic Environmental Initiative'' that would ''establish a coordinated global program to accomplish the strategic goal of completely eliminating the internal-combustion engine over, say, a 25-year period.''

Think about that. How long could you afford to get to work as gasoline steadily disappeared? How many years would your company last? What would your house be worth once nobody was working? And eventually, what would you eat?

I wouldn't say the cure is worse than the disease, because we don't know that. But it's so lethal to our political and economic liberties that we must be absolutely sure of the diagnosis before we commit ourselves. And the current state of science doesn't provide any such certainty.

Linda Seebach is the editorial-page editor of the Valley Times and San Ramon Valley Times.

Pub Date: 4/08/97

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