Heated debate over global treaty Warming: On the eve of a diplomatic summit in Japan, experts are split over a proposed agreement of 150 nations to curtail gases will it avert a disaster or create one?


November 30, 1997|By Timothy B. Wheeler | Timothy B. Wheeler,SUN STAFF

All across the Arctic, from Alaska to Scandinavia, glaciers have been retreating for the past century. Farther south, sea level has risen about a foot over the same time period, and severe rainstorms across the United States have increased about 20 percent.

As diplomats from 150 nations gather in Kyoto, Japan, to wrangle over what to do about global warming, these gradual changes may be harbingers of the slowly building environmental disaster long predicted from the increasing burning of fossil fuels.

Or, to hear some skeptics tell it, they may be completely normal jigs in the ebb and flow of the Earth's complex climate.

Two years ago, a United Nations study involving 300 scientists from around the world concluded that the 1-degree Fahrenheit increase in the earth's surface temperature over the past century is "unlikely to be entirely natural in origin." The Intergovernmental Panel on Climate Change, as it was called, said that despite uncertainties, "the balance of evidence suggests a discernible human influence on global climate."

Now, on the eve of the 10-day talks in Kyoto, the evidence is not much stronger as nations mull whether to sign an enforceable treaty to curtail emissions of carbon dioxide and a handful of other gases tied to the warming.

Opponents of the treaty warn of economic disaster if it is signed, predicting soaring fuel prices and industrial stagnation.

But among most scientists, the debate has largely shifted from whether warming will occur to focus on how much warmer it will get and whether the consequences will be major or mild.

Jerry D. Mahlman, director of the geophysical fluid dynamics laboratory at Princeton University, wrote in the journal Science that uncertainties remain in how global warming will occur because of weaknesses in the computer-driven mathematical models used to predict it. Nonetheless, the basic conclusion remains unchanged.

"We don't know exactly how it's going to happen," he adds in an interview, "but ain't anything going to make it go away."

It is beyond dispute that over the past 150 years, there has been a buildup in the Earth's atmosphere of carbon dioxide, methane and a variety of other gases related to human activity. These gases, along with water vapor, trap the sun's warming infrared rays close to the planet's surface much as glass does in a greenhouse.

This "greenhouse effect" was first posited in 1896 by a Swedish chemist, Svante Arrehnius, who predicted that carbon dioxide emitted by the coal-burning factories of his era could eventually warm the planet.

Carbon dioxide, which accounts for more than half of man-made greenhouse gases, has risen 25 percent since pre-industrial times in the mid-18th century. Another gas, methane, released by cattle, plant decay, rice paddies and coal mines, has doubled.

For such a significant buildup of gases, the surface temperature has increased only modestly -- about 1 degree -- prompting some to question the accuracy of the computer modeling.

"It's possible that human influence is no problem at all," contends Richard S. Lindzen, a meteorologist at Massachusetts Institute of Technology and a vocal critic of the U.N.-sponsored scientific report. "What I find disturbing is there's so little science and so much hype."

Other researchers see the evidence mounting, bit by bit. A study lake and ocean sediments, tree rings and retreating glaciers in the Arctic, published in Science earlier this month, has found that a warming trend that began 400 years ago has accelerated in the past 150 years.

Though natural factors, such as declining volcanic activity, drive the overall rise in Arctic temperatures, scientists with the National Oceanic and Atmospheric Administration concluded that gases released by human activity since 1920 have exaggerated the process.

A new report released last week by the U.N.-sponsored scientific panel stresses that warming will not be uniform, nor will it be harmful everywhere.

In the Northern Hemisphere, for instance, emissions from power plants and industry have been great enough to offset the warming due to greenhouse gases. Clouds and haze block sunlight, dampening its warming effect.

And in temperate regions, crop yields are likely to improve, thanks to the increased carbon dioxide levels responsible for warming. Higher average temperatures will also extend the growing season.

But harvests may suffer in tropical and subtropical latitudes, where some crops are already near their maximum tolerance for heat. Droughts and water scarcity will probably worsen in arid regions, notably the Middle East and northern and southern Africa.

Water, like air, expands as it warms up, and rising sea level is likely to inundate coastal areas, where 46 million people worldwide already live at risk of storm surges, the report says.

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