Let's not wait for `proof' on warning of global warming

Drought. With record temperatures scorching the nation, it's been front-page news this month. It's the worst dry spell since the '30s Dust Bowl for the Midwest. It has withered cotton in the South and set farmer against city-dweller in California. Across the nation, it threatens to raise food prices. But another news item this month, while less prominent, may turn out to be more significant. A report from the World Meteorological Organization (WMO), a United Nations agency, zeros in on the global warming trend. After centuries of stable climate, it says, we're slowly heating up. Probable reason: The greenhouse effect, whereby gases released into the atmosphere (largely from burning fossil fuels) trap the sun's heat. The changes seem small - a few degrees over decades. But the effects could be massive, as agricultural zones migrate, sea-levels rise, rainfall patterns shift, permafrost melts, and deserts expand.

Reading these two news items separately, we might not link them. Should we? Is today's drought a warning shot fired across the bow of an energy-wasting society? Is it just a coincidence that four of the hottest years in the past century have occurred in the 1980s - and that 1987 was the hottest on record?

The short answer is that no one knows. Even George M. Woodwell, director of the Woods Hole Research Center and a contributor to the WMO report, won't speculate. He longs to sound the alarm about the greenhouse effect. But he refuses to fasten it to the nation's two-year-long dry spell. ``Whether this particular drought is due to the warming of the earth as a whole is hard to say,'' he says. ``There is no proof - and there never will be.''

``No proof.'' The words echo like a mantra through late-20th-century consciousness. You hear them all along the boundary where scientific knowledge meets social policy. Is smoking unhealthy? ``No proof.'' Is acid rain destroying forests? ``No proof.'' Is the ozone layer being destroyed? ``No proof.'' Does dumping garbage at sea pollute the oceans? ``No proof.''

One can often sympathize with this answer. Science thrives on rigor, and scientists whose research offers no solid proof must be respected - even applauded - for saying so. But must society, then, take no action until science establishes irrefutable cause-and-effect relationships? Must a probable cause of environmental damage be considered utterly innocent until proved guilty?

Most of the time, we answer ``Yes'' - as though we were in a court of law, trying human suspects, withholding judgment until the last tittle of evidence is in. Science, however, doesn't operate that way. It builds slowly toward broad understandings that only rarely are framed as ``either-or'' propositions.

And that frustrates policy-makers. Some of them, sadly, respond with end runs around scientific research - using selective data, stretching conclusions, loading questions, or searching out dubious experts to say what they want to hear. The resulting shouting matches produce still more delay, as still another committee studies the problem.

On many pressing issues, we don't need to change our committees. We need to change our metaphor. We need to stop looking at environmental issues as though they were court cases. We need, instead, to think of ourselves as homeowners buying insurance. You don't insure against the absolutely predictible. You protect against the possible. Nor do you wait to establish causality. You recognize that ownership - and stewardship over the environment - involves risk-taking. So you defend yourself against large and irreversible damages.

Does that compromise principle? Not if the principle is to accomplish the greatest possible good under the circumstances. The circumstances are those of an increasingly complex, changeable, and fast-paced world - and an inertia of human institutions that may never let us know, with full certainty, all we need to know.

So what of drought and the greenhouse effect? We can't prove they're related. So shall we, like stolid jurists, do nothing? Or, like homeowners, shall we listen thoughtfully to the warnings, assess the circumstantial evidence, and take basic steps to insure against further damage?

Shall we, as the Iowa corn withers and the Sahara expands, make serious changes in our fossil-fuel use? Or shall we appoint another committee?

A Monday column

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