Global Warming Creates a Climate of Uncertainty : Environment: We may be overstating the problem or understating it, a scientist says. Some areas could benefit.
As more than 130 nations forge ahead to enact an unprecedented treaty this summer to reduce future global warming, scientists and economists remain uncertain about just what kind of world the so-called greenhouse effect would produce.
“When you first look into climate change, you realize how little you know,” said Ralph Cicerone, an atmospheric chemist at UC Irvine. “The more you look into it, the more you realize how little anyone knows.”
In many ways, the doubts are not unlike those that haunted nations in Montreal five years ago when they approved an agreement to reduce the use of ozone-destroying chemicals called chlorofluorocarbons, or CFCs.
As with global warming now, the evidence that CFCs were destroying the ozone shield was largely theoretical in 1987. A hole in the ozone layer over Antarctica had already been observed, but there was no conclusive proof that it was caused by CFCs, used as refrigerants and propellants in aerosol cans.
As it turned out, one crucial scientific prediction about the ozone layer proved wrong. The shredding of the shield that protects the planet from harmful ultraviolet radiation is occurring at least twice as fast over most regions as computer models had predicted. Millions more people are expected to get skin cancer as a result.
Climate change could be even more devastating. Rising seas could inundate island nations, wipe out rich coastal marshlands and create millions of environmental refugees. Many species of wildlife probably would vanish.
But until scientists better understand how various natural systems interact and influence climate, they cannot sketch these kinds of scenarios with strong confidence. How fast will the planet warm? How much? What will happen on a regional level? Many answers remain maddeningly elusive.
“We may be overstating the problem. We may be understating the problem,” said Robert Watson, a National Aeronautics and Space Administration scientist and program manager who organized aircraft campaigns to study the ozone hole. “That’s what makes it a very difficult situation for government and industry.”
Moreover, the changes needed to reduce warming could demand an overhaul in lifestyles around the world, not in just one industry. The price tag, while expected to be significant, remains unknown. Some economic models project staggering costs, others financial windfalls.
Like the Antarctica ozone hole, recent warming may signal the beginning of global change. Or it could just be a result of natural climatic variability. Over the past century, the average global temperature has risen half a degree Fahrenheit.
“I think (global) warming has already begun, but I just can’t convince myself that there is proof of it,” said UC Irvine’s Cicerone.
In United Nations-sponsored negotiations, the United States and other industrialized nations are discussing whether to stabilize carbon dioxide emissions at their 1990 level. Such a move, depending on how many nations agree to it, probably would make only a small dent in eventual warming.
Environmentalists and many scientists support the step simply because it would establish a vehicle for future reductions as scientific and economic doubts are resolved. Whatever action is agreed upon would be ratified at a global environmental summit in Brazil this June.
Carbon dioxide, produced by the burning of oil and other fossil fuels, traps heat in the atmosphere, much like the panes of a greenhouse. Man-made carbon dioxide is the biggest contributor to potential global warming.
Most scientists agree that a continued pumping of carbon dioxide and other greenhouse gases will warm the Earth. A U. N. scientific panel has estimated that temperatures would rise 4 to 8 degrees Fahrenheit by the end of the next century if emissions continue unchecked.
That may sound small, but the difference between ice ages and current temperatures is only about 10 degrees Fahrenheit.
“Carbon dioxide causes the climate to attempt to warm up, and that is a piece of physics we understand really well,” said Jerry Mahlman, a government scientist and climate researcher. “How the Earth responds determines how much it warms up, and oceans, clouds and ice all affect that.”
The reaction of these natural systems cannot be predicted with “very high skill,” he said.
For instance, just a small change in clouds could enhance or “completely offset” the greenhouse effect, said Warren Washington, director of the Climate and Global Dynamics Division of the National Center for Atmospheric Research in Boulder, Colo.
Scientists just recently discovered that sulfate aerosols, produced by the burning of coal, are helping create clouds that have a cooling effect. These aerosols may have masked global warming in the last 40 or 50 years. As the sulfates are phased out to eliminate acid rain, warming may increase.
Until recently, CFCs also were seen as a major contributor to global warming. But some scientists now believe that the depletion of the ozone layer caused by CFCs may have a slight cooling effect.
At this point, scientists do not even know where all the man-made carbon dioxide is going. Only about 60% of what is released in a year winds up in the atmosphere. The rest may be absorbed by soil, plants or the oceans.
Greenhouse skeptics, citing the ambiguity, argue that nature may somehow be able to absorb increasing amounts of carbon dioxide through such means as accelerated plant growth. Environmentalists counter that the absorption could be less in the future, causing temperatures to warm at an even faster rate.
In any case, scientists need to know where the carbon dioxide is going to predict more accurately future amounts in the atmosphere.
James Hansen, director of NASA’s Goddard Institute for Space Studies, says the range of predicted temperature increases must be narrowed before scientists can tell the world what to expect.
“If (the warming) is near the low end, it’s a very different story than if it’s at the high end,” Hansen said. “If it’s at the low end of the range, it would be practical for us to adjust to it with a reasonable level of inconvenience.
“But if it is at the high end, then it’s going to take really dramatic changes that will completely change lifestyles.”
If temperatures change as much as 8 degrees, the planet would become warmer than it has been in millions of years.
At the low range, Earth would warm at a rate five to 10 times faster than at any time in the past 10,000 years, producing the warmest temperatures in more than 100,000 years.
“The real impact is going to come from the extremes, the hottest days to the nights when it doesn’t cool off,” said Cicerone, noting there probably would be a rise in heat-related deaths.
The world’s ability to adjust to climate change will largely depend on how fast warming occurs.
“The problem with global warming is not having a warmer Earth,” said John Firor, director of advanced studies at the National Center for Atmospheric Research. “If you look back over geological times, the Earth has been sometimes warmer and sometimes cooler. . . . What we need to do is make sure we don’t force a climate change that is too fast for natural systems to adapt to.”
For instance, a warming trend in the 12th Century carpeted Greenland with forests. Northern Europeans colonized the now icy outpost. A few hundred years later, Firor said, temperatures dropped and Europeans changed the kind of grains they planted.
“Those changes didn’t produce a lot of hardship because people had a lot of time to make the adjustments,” Firor said.
Forecasters generally predict that seas will continue to rise. Some agricultural regions would become prey to new kinds of pests as temperatures climb.
Many species would vanish if the climate changed too rapidly for them to escape to more favorable settings or if barriers, such as mountains or cities, restricted their paths.
If sea ice disappeared, as suggested by some scientists, Arctic mammals, including the polar bear, would be threatened.
But the impact largely remains a question mark because forecasting climate change by region or locality is even more difficult than predicting the size or rate of warming.
Although the average global temperature would rise, temperatures would not be uniformly higher around the world. Some places would get warmer, others cooler. Some would get more rainfall, others less.
Mathematical models agree that the poles would heat up faster than lower latitudes, particularly in the winters. The centers of continents, such as the U. S. Midwest and the central part of southern Siberia, would have hotter and drier summers.
But the “real questions,” said Washington, are whether deserts and rain belts will move, whether droughts will become more frequent.
“The bind we’re in is that it is very hard to figure out which of these possibilities are real or not,” Cicerone said.
Unlike ozone depletion, which benefits no one, global warming could conceivably improve the living conditions in parts of the world. Some regions, for instance, might have longer growing seasons.
Because of the unknowns and the potential costs, Michael E. Schlesinger, a climate scientist at the University of Illinois, believes an international accord to stabilize emissions would be “a little premature.”
“I have been concerned for some time that if we behave in a certain way and it is later found out that the problem is less acute, then we will lose credibility and there will be a backlash,” Schlesinger said. “And that will be the worst of all outcomes.”
Schlesinger published a study last year that concluded that waiting a decade to curb greenhouse gases would not significantly affect world temperatures. A delay would mean a temperature difference of less than 5% of what it would be if steps were taken immediately, he wrote in the scientific journal Nature.
But Schlesinger’s views appear to represent those of only a minority of scientists. Others say the evidence justifies taking action now to reduce greenhouse gases, if for no other reason than to curb air pollution and improve energy efficiency.
“I think most scientists would agree that stabilization (of greenhouse emissions) is a good goal,” said NASA’s Hansen.
Given the consensus, why has so little been done to reduce greenhouse gases?
One answer is that the ramifications are not immediately felt. It is politically more difficult to induce people to make sacrifices now for a problem in the future.
A lag--possibly of several decades to a century--exists between the time greenhouse gases are released into the atmosphere and the actual warming. Oceans take time to heat up and affect global temperatures.
“It’s a tough problem for policy-makers because they are always behind the curve,” said Jessica Mathews, an environmentalist. “You are never at the moment feeling the effect of what has been done. . . . You don’t have this lag with ozone depletion.”
Even more daunting may be the price of reducing greenhouse gases. Everyone who consumes energy, everyone who drives a car would have to make changes. What that would cost is disputed.
The Bush Administration blames the murky science and economics for its reluctance to commit to stabilization.
“There is uncertainty about the scientific benefits and uncertainty about the costs,” said Robert Reinstein, the United States’ chief negotiator in the U. N. talks on global warming. “Add all that up and the conclusion we come to is that (stabilizing carbon dioxide emissions) doesn’t make sense for us.”
Administration officials say their economic models show that the price of stabilization is prohibitive. Critics of the U. S. position counter that the Bush Administration’s economic models assume unrealistically high future economic growth, thereby inflating the nation’s energy needs.
Projecting lowered growth, however, could be politically risky in an election year.
Several studies have examined the costs of reducing beyond 1990 levels. A U. S. Department of Energy report said the nation would pay as much as $95 billion annually and require a doubling in the price of gasoline to cap carbon dioxide emissions at 20% below 1990 levels by the year 2000.
Conversely, a panel of the National Academy of Sciences has said the United States could reduce greenhouse gases by as much as 40% at little or no extra cost.
Even more optimistic was a study by environmental groups and the Union of Concerned Scientists. It found that carbon dioxide emissions could be slashed 25% by the year 2005 and more than 70% by 2030 at a net savings of $2.3 trillion.
Economists attribute such widely disparate projections to different assumptions made by the economists, different economic models and different questions being asked in the studies.
Some measure the cost of reducing only carbon dioxide. Others also look at reducing other greenhouse gases, such as methane and nitrous oxide.
Some assume carbon dioxide is reduced primarily through a large tax on energy. Others assume it is reduced through direct limits on emissions.
Reinstein, the U. S. negotiator and deputy assistant secretary of state, said that some analyses suggest that adapting to global warming--planting different crops or shoring up coastlines against sea level rise--could be less expensive than reducing the gases.
Environmentalists scoff at this notion.
“If you don’t control emissions,” counters Rafe Pomerance, senior associate of the World Resources Institute, a Washington-based environmental think tank, “you have to adapt to constantly changing conditions. . . . The Earth will warm indefinitely.”
Roger Brinner, executive director of DRI/McGraw-Hill, a business consulting firm, believes the United States could stabilize emissions of carbon dioxide and other greenhouse gases without sacrificing standards of living--if policy-makers were “super-smart.”
Brinner advocates a combination of tree-planting (trees absorb carbon dioxide), subsidies for energy-efficient appliances, automobiles, light bulbs and factory equipment, and energy taxes. The tax revenue could reduce the national deficit and pay for investment tax credits, he said.
But Brinner does not favor a stabilization policy. “I don’t have a hell of a lot of confidence that we would do it right,” the economist said.
In time, both the scientific and economic ramifications of climate change are expected to become clearer.
Some scientists believe a series of satellites to be launched by NASA in this decade will help detect changes that could improve the accuracy of climate models.
The models, while still crude, already have been refined through better computer technology and scientific research.
On the economics side, researchers predict that the eventual costs of slowing global warming could be substantially reduced through an aggressive research and development program to improve energy efficiency.
“People are scared to death by this,” said Mahlman, the climate researcher and director of a U. S. geophysics laboratory. “They are scared if they do nothing, they will look like idiots, and scared if they do something significant, it will amount to trying to change the whole world around. And both are true.”
A Look at the Future
The International Panel on Climate Change of the World Meteorological Organization and the United Nations Environment Program offers these possible scenarios for changes by the year 2030. The scientists, who predict the average global temperature will rise by 3.24 degrees Fahrenheit, say forecasting regional climate changes is extremely difficult. Here are some rough possibilities:
1) Central North America
Warming: Would vary from about 3 to 5.5 degrees Fahrenheit in winter and 3.5 to 5.5 in summer.
Precipitation: Increases would range from 0% to 15% in winter, with decreases of 5% to 10% in summer.
2) Southern Asia
Warming: Would vary from 1.5 to 3.6 degrees Fahrenheit throughout the year.
Precipitation: Would change little in the winter but generally increase throughout the region by 5% to 15% in the summer.
3) Sahel
Warming: Would range from 1.5 to 5.5 degrees Fahrenheit in this area south of Africa’s Sahara.
Precipitation: Would increase overall.
4) Southern Europe
Warming: Would be about 3.5 degrees Fahrenheit in winter and would vary from 3.5 to 5.5 degrees Fahrenheit in summer.
Precipitation: Some indication that there would be rain in winter but summer precipitation would decrease by 5% to 15%.
5) Australia
Warming: Would range from 1.5 to 3.5 degrees Fahrenheit in the summer and about 3.5 degrees Fahrenheit in winter.
Precipitation: Would increase by about 10% in the summer.
Warming Gases
The contribution from each of the human-made greenhouse gases to global warming from 1980 to 1990.
Carbon Dioxide: 55%
CFCs 11 and 12: 17%
Methane: 15%
Other CFCs: 7%
Nitrous Oxide: 6%
