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Ideas & Trends: Global Waffling; When Will We Be Sure?

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September 10, 2000, Section 4, Page 3Buy Reprints
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WHEN several eminent scientists returned recently from a tourist cruise to the North Pole aboard a Russian icebreaker and reported finding water, not ice, at the top of the world, the image resonated far and wide, providing a call to arms for scientists and environmentalists who for years had been trying to convince politicians and the public that heat-trapping gases from tail pipes, power plants, even methane-belching cattle, could disrupt the climate.

But on second look, things were not nearly so simple. Although arctic experts said there were many signs of warming, including a thinning and shrinking of the polar ice cap, there was no way to link a patch of sun-dappled water at the pole to climate change.

So the question of what is happening to climate -- and whether people or natural forces are to blame -- returned to the realm of nuanced, statistical fuzziness, where it has been for nearly 20 years.

What a moment to lose potential clarion calls. Hundreds of negotiators from industrialized countries are to convene this week in Lyon, France, and again in late November in The Hague to try to firm up ways to cut emissions of greenhouse gases under a 1997 climate treaty called the Kyoto Protocol. The treaty was signed by the United States and 84 other countries but is in danger of falling apart because of disagreements over how to make and measure cuts.

Most climate experts are certain that global warming is real and that it threatens ecology and human prosperity, and a growing number say it is well under way. But policy makers, always eager for black and white, have once again found science offering shades of gray.

Indeed, global warming is a classic example of the persistent mismatch between the language of science and the needs of policy.

Science operates by steadily chipping away at ideas through experiments or observations, eventually revealing truths, but often obliquely -- by eliminating what is not true. The bigger the idea, the harder it often is to verify with precision. The result is persistent debate, whether the issue is how to manage forests to reduce wildfires, how to set limits for chemicals in food to prevent cancer, or -- in this case -- how to figure out whether people are dangerously fiddling with the global thermostat.

But before policy makers can try to sell potentially costly or difficult solutions, say, taxing fossil fuels, they need to build a clear and compelling case that strong action is called for.

The lesson in all of this, according to climate scientists -- some of whom think humanity is already in big trouble -- is that no one should expect some alarm bell to start ringing to summon societies to take action.

The evidence is subtle and complex, and probably will be so for a long time to come, said Jerry D. Mahlman, who is retiring as director of the federal Geophysical Fluid Dynamics Laboratory in Princeton, N.J. ''This is going to be incremental forever,'' he said.

Those increments continue to add up, he and other climate experts said. Past climate ups and downs mostly mesh well with natural variations in the brightness of the sun or the cooling effect of parasol-like plumes of particles spewed by big volcanoes. But the recent warming, according to several recent studies, only correlates well with one thing: the buildup of carbon dioxide, methane and the other greenhouse gases.

Hints that warming is being caused by emissions from industry and other human activities have been extracted from air bubbles trapped in ancient ice, from variations in tree rings, from the quick retreat of alpine glaciers. Thermometers dropped deep in the ocean and in holes bored in permafrost show warming patterns that do not match up with natural influences like changes in the sun's brightness.

STILL, the subtleties have allowed warming skeptics ample opportunity to challenge the idea. Some, like Richard S. Lindzen, a meteorologist at the Massachusetts Institute of Technology, have built durable counterarguments, saying the links connecting the earth's oceans, air and ''cryosphere,'' its frozen places, are impossible to elucidate with sufficient confidence to predict much beyond next week's weather.

In an interview, Dr. Lindzen acknowledged the arctic warming trend and slight global warming measured in the last century, but said it all is well within the realm of natural variation or measurement error -- and not yet within our power to understand.

''This is a field that was in a primitive state when it assumed a policy importance a few years ago,'' Dr. Lindzen said. ''Suddenly we've declared thousands of people in a primitive field as world experts, and they're trying to have their day.'' And reports last week that boats had traversed the normally frozen Northwest Passage and northern rivers and lakes were freezing later and thawing earlier were countered with the response that this seeming meltdown could still be ascribed to natural wiggles in temperature or ocean currents.

But most scientists, including some who work with Dr. Lindzen at M.I.T., say the balance of data has shifted firmly toward a conclusion that people, through their impact on the atmosphere, are influencing climate now and will have even more impact in coming years.

Somehow, many experts say, if the threat is to be countered, societies will have to figure out a way to act in the face of gray uncertainty, to deal aggressively with a problem that lacks the attributes of a crisis. That is no easy task.

Dr. Mahlman has pretty much given up on that hope, saying that many countries, including the United States, have essentially decided that the focus is going to be on painless, low-cost fixes like growing trees to sop up the most common greenhouse gas, carbon dioxide, and on adapting to coming warming instead of countering it.

''We just don't want to face up to it,'' he said, adding that people do not want to change their lifestyle or the economy ''for the sake of avoiding future costs.''

He and others stress that the real challenge with global warming and similar issues is that, by the time the impact becomes too clear to debate, it will be far too late to do anything about it.

A version of this article appears in print on  , Section 4, Page 3 of the National edition with the headline: Ideas & Trends: Global Waffling; When Will We Be Sure?. Order Reprints | Today’s Paper | Subscribe

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