The heat is on: as evidence of global warming mounts, President Bush tries to balance the environment's health with the economy's. (National).

When it comes to global warming, who's feeling the heat? One answer: most everyone on Earth. But in the sense of being pressured to act, President George W. Bush has stayed cool.

Last year, national and international panels of hundreds of climate experts agreed that most of the warming during the past 50 years has probably been caused by people, mainly through burning coal and oil--creating carbon dioxide, a gas that traps heat in the air like a greenhouse roof.

The warming has intensified from the 1990s through today. The year 2001 was the second-warmest ever recorded, below only 1998. This year is expected to be hotter still. If people keep pumping out billions of tons of the so-called greenhouse gases each year, as we've been doing for decades, temperatures could rise 3 to 9 degrees this century, many scientists say, potentially leading to devastating droughts and floods.

The solution might seem a no-brainer: Stop producing those gases and the problem goes away. Last fall, 180 nations approved the Kyoto Protocol, a treaty that would require rapid cuts in greenhouse-gas emissions. But there are deep divisions of opinion on such a global problem. One camp seeks to forestall catastrophe with strict limits on pollution. The other--including the President--sees peril in doing too much.

Bush, alone among major world leaders, rejected the Kyoto Protocol, saying he would come up with a better approach for the U.S. In a Valentine's Day speech, the President announced his plan. He would encourage voluntary changes for companies designed to limit, but not halt, the growth in the gas emissions. A progress report would be done in 2012, and more-stringent measures might kick in, if warranted.

The environmental threat remained uncertain, Bush said, but the economic harm from rasher actions was clear. If he agreed to the stricter Kyoto proposals, Bush said, the cost to bring industry and consumers into line could hit $400 billion.

Support for the President has come from a few climate scientists who think the dangers of warming are overstated, and frond industries that emit lots of greenhouse gases, mainly carbon dioxide, or sell products that do so, like SUVs.

But many experts say they are shocked. After analyzing Bush's policy, they say it almost guarantees a hotter future in which ecosystems and many countries will suffer.

The critics include Ralph J. Cicerone, an atmospheric scientist at the University of California at Irvine, who chaired a National Academy of Sciences panel that provided advice to the White House last year. Cicerone says it's a mistake to use uncertainty in the science as a reason to take a relaxed approach to global warming.

Continued growth in emissions of heat-trapping gases, Cicerone says, will inevitably make any risks greater. "This situation is not sustainable and its trajectory is toward dangers," he says, adding that the White House proposal "lacks ambition and foresight. It sets goals that are too timid."

FINDING COMMON GROUND

One way to navigate the debate is to look first at what virtually everybody currently agrees on. No one doubts any more that the average surface temperature on Earth is rising, and that humans have, in little more than a century, increased the atmosphere's natural greenhouse effect.

Some scientists say the human influence is minimal compared with natural variations in the sun's intensity and other shifts, but no one denies that humans are fiddling at least a little with the thermostat (see "Cranking Up the Thermostat," page 16).

We've done this mainly by burning things, lots of things, to feed industrial growth: first went forests, then tens of billions of tons of coal and barrels of oil, fuels that release carbon dioxide.

That gas--along with water vapor, methane, and other substances--allows sunlight into the atmosphere to warm things, but it also holds in some of the escaping heat at night. If not for this natural greenhouse effect, the planet would be an ice ball. Instead, it has an average temperature of nearly 60 degrees.

Many scientists say people have upset the normal balance. Forests can grow back and absorb carbon dioxide. But once the carbon in coal and oil is released, most of the resulting gas stays in the air for decades. The result? After remaining basically constant for thousands of years, levels of carbon dioxide in the air have risen 32 percent in just the last 150 years.

There is another point that everyone agrees on. Carbon dioxide makes this an extremely difficult problem to solve. It is a basic byproduct of modern life. Every coal-fired power plant, every SUV, is part of the problem. Flipping on the lights, surfing the Web, doing anything with electricity contributes to it.

It's the tight link between carbon dioxide and industry that has powerfully influenced President Bush's decision. The U.S., with the world's biggest economy, is also the biggest source of carbon dioxide, producing about a fourth of the global total.

Deep cuts in emissions would disrupt the economy, but allowing the economy to grow would actually help the environment, the President said. That could lead to new technologies needed to end our dependence on coal and oil-technologies like safer forms of nuclear power and hydrogen fuel cells (see "Your Next Car?" opposite page). "My approach recognizes that economic growth is the solution, not the problem," Bush said in his speech.

WAITING FOR A SOLUTION

The planet can afford to wait as those technologies develop, the Bush administration and some scientists maintain. They argue that climate models predicting big changes are poor simulations of the Earth, and that the atmosphere, ecology, and oceans have a large capacity to absorb the human influence. As one senior White House official says, "There is headroom."

But the Bush administration is accused of doing what's best for the energy industry, regardless of what's best for the environment. Bush himself is a former oil executive who took campaign contributions from energy companies. Eric Schaeffer, a top enforcement official at the Environmental Protection Agency, recently quit, saying he was fighting a White House that was undermining the EPA's pursuit of industrial polluters. "It's this bunch of guys in energy who say, `Boo! We don't like this,'" Schaeffer says, "and the Bush administration says, `Well, they elected us.'"

The stakes may transcend politics. A rise of a few degrees might not seem like much. But the average global temperature now is only about 5 to 9 degrees warmer than it was in the depths of the last ice age, 18,000 years ago. More warming would likely change storm and drought patterns, threatening wildlife, water supplies, and tropical agriculture, most authorities say. Seas could rise a foot or more, swelled by melting glaciers and the expansion that occurs when water is warmed.

Many experts say the risk is big enough to be worth investing money now to stem the emissions that are the root of the problem, even if it costs billions of dollars.

"The science is already telling us that our interference with the climate is unprecedented and that we are already heading for dangerous impacts," says Peter H. Gleick, president of the Pacific Institute for Studies in Development, Environment, and Security. "The good news is that there are many things we can, and should, be doing right now to reduce greenhouse-gas emissions that are cheap, effective, and smart. The bad news is that the President's plan does none of these things."

Cranking Up the Thermostat

At the beginning of the Industrial Revolution, the Earth's average temperature was relatively cooler. As industry has expanded, and the resulting carbon dioxide emissions have increased, the global thermometer has risen as well. Here's how each year's temperature has varied from the average global temperature in the period from 1880 to 2001.

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Your Next Car?

The car of the future may need no gasoline. Earlier this year, General Motors unveiled its Autonomy concept car (far left). A fuel cell (left) would power the car, emitting only water and heat by relying on hydrogen instead of gas. Major automakers are touting the cell as an answer to environmental concerns. The technology could, in principle, be as useful in supplying power to homes and industry. GM hopes to produce a working model of the Autonomy by the end of the year. --Danny Hakim

[ILLUSTRATION OMITTED]

Global Hot Spot

Though temperatures have risen over much of the world, certain areas have heated up more than others. Circles on the map show the difference between 2001 temperatures and 1961-1990 averages. Figures are not available for areas with no circles.

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ANDREW C. REVKIN is a Times science writer specializing in the environment and author of Global Warming: Understanding the Forecast.

The Heat Is On

FOCUS: Why President Bush Rejects the Call to Sharply Cut Global-Warming Gases

TEACHING OBJECTIVES

To help students understand the debate over global warming, specifically whether emissions of carbon dioxide and other substances from the U.S. and other industrialized countries are causing Earth's temperature to rise to potentially dangerous levels.

Discussion Questions:

* Why do you believe some scientists disagree with the generally accepted concern about global warming?

* Do you believe President Bush's call for a voluntary cut in the growth of emissions will work?

* Do you agree with President Bush that pursuing economic growth will lead to a healthy environment?

CLASSROOM STRATEGIES

Critical Thinking/Debate: Review the arguments that the cost of cutting emissions of greenhouse gases is too high and that the science linking greenhouse gases and global warming is uncertain. Then note the observation of atmospheric scientist Ralph Cicerone, who says that uncertainty in the science is not a reason to take a relaxed view on the dangers of global warming.

What is Cicerone saying? If he and other proponents of cutting emissions cannot prove that the threat is real, do they have a right to criticize President Bush's voluntary approach? Next, discuss President Bush's position. If he and his supporters cannot prove Cicerone and others who want emissions cuts are wrong, do they have a right to gamble that global warming is not the threat it is said to be?

Remind students that the U.S.--with about 6 percent of Earth's population--produces about a quarter of its carbon dioxide. How would students defend or rebut other countries' often-heard argument that the U.S. uses more than its fair share of Earth's resources? Class Vote: Suppose Americans are asked to vote in a referendum on cutting emissions of greenhouse gases. The catch: A serious cut in emissions would cost the average American family about $300 a year to pay for new anti-pollution technology. How would students vote? Students might discuss the idea with their parents and report back on how their parents would vote in such a referendum.

QUIZ 2 use with National, pages 14-17. Multiple Choice

1. The burning of coal and oil produces gas that traps heat in the atmosphere. Which of the following is the major greenhouse gas? (a) ether (b) hydrogen (c) carbon dioxide (d) fluoride.

2. The agreement by 180 nations to cut emissions of greenhouse gases is called the (a) Berlin Pact (b) Japan Decision (c) European Agreement (d) Kyoto Protocol.

3. President Bush opposes across-the-board cuts in the emissions, but he does support (a) cuts in the steel industry (b) cuts in oil burning (c) voluntary limits in the growth of gas emissions (d) voluntary cuts to halt some emissions.

4. The President says the way to end dependence on Coal and oil is to develop new technologies. And the way to do that, he says, is to (a) cut imports of foreign technology (b) expand imports of foreign technology (c) increase taxes on heavy industry (d) pursue economic growth.

5. Scientists who are concerned about global warming warn that continued release of greenhouse gases could produce widespread floods as seas rise, in part because of (a) glaciers melting (b) rivers changing course (c) wells overflowing (d) rain diluting the oceans.

6. The region with the greatest concentration of warming temperatures is (a) Central America (b) Australia (c) Europe (d) Africa.

7. Efforts to cut greenhouse gases include redesigning auto engines. The car of the future might be powered by a fuel cell that runs on (a) hydrogen (b) water (c) peroxide (c) alcohol.

ANSWERS

1. (c) carbon dioxide. 2. (d) Kyoto Protocol. 3. (c) voluntary cuts in growth of gas emissions. 4. (d) pursue economic growth. 5. (a) glaciers melting. 6. (c) Europe. 7. (a) hydrogen.