But the persistence of such uncertainties is no justification for misusing them, as some self-styled and self-serving skeptics do, to dispute more fundamental and established facts: that the earth is warming in a rapid and abnormal way, that burning of coal, oil and natural gas is largely to blame, that the need to reverse this trend is urgent.

Notable among these challengers are George W. Bush and his environmental advisers, who offer a view even the oil companies and automakers have abandoned. The earth's warming trend has been clearly established, they say, but the causes have not -- and therefore the responses can largely be postponed.

It's an argument that may be comforting to voters who sense a day of reckoning over the energy-gobbling American lifestyle and wish to postpone it. But the room for making this case has been narrowed again by the Intergovernmental Panel on Climate Change.

In its third consensus report on global warming, this group of top climate scientists has concluded that world temperatures may rise much farther and faster than seemed probable just five years ago. The panel has also abandoned its earlier hedging about human causation, asserting that greenhouse gases from industry and autos have "contributed substantially to the observed warming over the last 50 years."

It is important to note that this panel is not on the cutting edge of climate science, but rather on its trailing end. Its assignment is to review research, not conduct it; its members come from a professional community devoted to disproof and rivalry, and from nations whose economies have much at stake. Its conclusions are subject to further review by hundreds of other scientists and more than 150 governments, all empowered to influence the final report.

That version will not be finished until early next year. But the draft, whose main assessments are considered unlikely to change, was slipped to news media in advance of next week's international conference on global warming. At that meeting, in The Hague, national governments will try again to work out ways of reducing greenhouse gases as envisioned by the Kyoto Protocol of 1997.

The questions before the delegates have only grown more contentious with time: How much reliance should be placed on recapturing emissions, rather than reducing them? How large a role should be given to market mechanisms, as opposed to government controls? And, biggest of all, how should cleanup responsibilities be apportioned among the nations?

But these questions have also grown more urgent, for reasons amply underscored in the intergovernmental panel's new forecasts. In the three years since the Kyoto agreement was reached, the prospects of catastrophe have grown worse, and yet no major industrial nation has ratified its terms.

The United States, which has contributed most to creating the problem, has not set the example it ought in adopting the protocol or changing its behavior. It is past time for Washington's delegates to lead the world in saying that humankind cannot wait for certainty on every nuance of global warming before taking bold steps to reverse its all-too-evident course.

© Copyright 2000 Star Tribune

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