Global Warming: The Debate Heats Up

John B. Shlaes is on red alert. As executive director of the Global Climate Coalition, a 55-member U.S. business group that lobbies to influence policy on climate change, he sees an imminent threat. In March, delegates from 118 nations are set to meet in Berlin for the most important conference on global warming since the Rio Summit in 1992, when they signed a global treaty to stave off climate change. Now, some nations want to amend the treaty to include steeper cuts in emissions of carbon dioxide and other, more far-reaching measures. "Some of these things could get passed," warns Shlaes. If so, "they will put the U.S. at a competitive disadvantage."

The global-warming hawks are led by 36 island states in the South Pacific, Indian Ocean, and Caribbean, which would be threatened by the rising sea levels that may accompany any warming. The 11-month-old treaty initially called for industrial nations to cut emissions of greenhouse gases voluntarily to 1990 levels by 2000. But the hawks have proposed that industrial countries, which spew out 48% of the world's CO2, reduce emissions an additional 20% beyond 1990 levels by 2005. Other measures put forth by various European countries, especially those likely to meet their goals, include imposing formal targets and timetables for reductions that extend beyond 2000 and setting international standards for technology.

The hawks argue that the more stringent measures are necessary because the current provisions are inadequate. Last year, the Intergovernmental Panel on Climate Change (IPCC), the body that evaluates global-warming research, announced that to stabilize the cumulative amount of CO2 in the atmosphere at even double current levels, man-made emissions would have to drop below 1990 levels. Then in February, U.N. officials reported that 9 out of 15 industrial countries, including the U.S., which had submitted plans to cut emissions under the current treaty, weren't going to meet their goals. In fact, Japan estimates that by 2000 its emissions will be 3.1% higher.

Tougher measures, however, even if ratified, may have little immediate impact. "Until industrial nations meet their current goals, more ambitious programs are sure to fail," says one Chinese official. China, India, and Saudi Arabia will be among the nations opposing stricter emissions standards. Moreover, since only 18 out of 36 industrial countries have filed their plans for cuts, policy-makers don't have enough data to move forward, say others. Then there's the cost: No one has studied the economic impact of a 20% cut, although a 1992 Stanford University study did conclude that the faster emissions cuts are made, the more expensive they will be.

"FINGERPRINTS." Even so, those calling for stricter standards say plenty of scientific evidence indicates a global warming may be under way. They cite everything from satellite-confirmed rises in sea level, recent increases in the frequency of the tropical El Nio climate systems, a rise in global temperatures of about 0.4C this century, and record high temperatures in the 1980s, which resumed last year after a three-year cooling. The recent relative change of recorded temperatures on the surface and in the atmosphere provides what James E. Hanson, head of NASA's Goddard Institute for Space Studies in New York, calls "evidence for the fingerprints" of a global warming.

Yet Hanson and others also agree with Thomas Karl, a scientist at the National Climatic Data Center, who says it is premature to draw conclusions. Scientists need a longer record of data such as surface land, water, and atmospheric temperatures, sea-level rises, and how much sunlight reaches the atmosphere. That, plus data on historical climate from coral, ice cores, and tree rings, will help them to determine whether warming is a long-term trend--and if it is, whether it's caused by natural forces or by man-made gases. "We're learning to distinguish the natural changes, and we know what it takes to do the detection," says Tim P. Barnett, an expert in detecting global warming at the Scripps Institution of Oceanography. "But it's hard to justify more draconian measures based on the information we have."

Scientists are improving climate models used to predict changes. Recent research has led to a better understanding of the role clouds play in absorbing sunlight, how much CO2 forests and oceans soak up, the cooling effect of pollution and volcanic eruptions, and historical climate. By plugging such information into the climate models, along with more recent data on greenhouse emissions, the models now predict lower potential warmings, about 2F to 4F, further into the future. Even so, predictions remain speculative, especially those involving any regional climate variations.

SMOKING GUN. Meantime, research continues to add new dimensions to the global-warming puzzle. By applying time-series analysis techniques he devised, David J. Thomson of AT&T Bell Laboratories recently found that in the middle of this century, just as CO2 levels were taking off, the timing of the earth's seasons was disrupted--they started earlier in some places, later in others. "The data suggest that the rate of drift in the annual cycle is unprecedented and appears to be correlated to the increase in carbon dioxide," says Jeffrey J. Park, associate professor of geology and physics at Yale University.

If Thomson's work pans out, it suggests that one effect of rising CO2 levels could be more unpredictable seasons. In any locale, the annual cycle of temperature is controlled either by the cycle of sunlight received there or the cycle of heat transported from elsewhere, the tropics, for instance. Thomson speculates that rising levels of CO2 may disrupt the balance of those cycles.

Thomson's work is sure to kick off debate and new research. But even scientists who believe a warming is under way concede it will be at least 5 to 10 years before they find the "smoking gun" or "guns" that signal it--and enough evidence to indicate that CO2 is the cause. Absent that ammunition, global-warming hawks are unlikely to muster enough political support for more expensive action--at least for now. But if, as some scientists predict, the mercury keeps rising, drastic measures could quickly become more politically fashionable.


A treaty to prevent global warming is just 11 months old, yet some countries want stronger action now, including a new 20% cut in emissions--despite a lack of compelling new scientific evidence:

-- Scientists don't know if recent climate changes, such as uarmer temperatures, are part of a long-term trend or whether they're natural or man-made

-- Climate models are becoming more sophisticated, but they can't yet reliably predict the effects of any global warming, especially regional variations

-- It is likely to take at least five years to find the "smoking gun" that signals any global warming

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