CLIMATE FEVER.

How to halt the heat

As pollution warms the air, scientists seek ways to cool it down.

Spring is usually prime chow time for some 1,200 polar bears along Canada's Hudson Bay. Each year they plunder the bay's ice floes, smash open the snow caves of seals, and stuff themselves on seal Pups. But in recent years the bears' feast has turned into slimmer pickings. Why?

Temperatures at Hudson Bay have risen by one half degree Fahrenheit every decade since 1950. Winter ice on the bay melts three weeks earlier than it did just 25 years ago, which means three fewer weeks of polar bear mealtime. Result: Polar bears are 10 percent thinner and produce 10 percent fewer cubs than they did 20 years ago. And thought climatologists (weather scientists) hotly debate the causes behind Earth's Arctic meltdown, "these changes are startling and unexpected," says James McCarthy, co-leader of the United Nations Intergovernmental Panel on Climate Change.

MELTING WORLD

The plight of polar bears is just the tip to the iceberg when it comes to mounting evidence of global warming--Earth's rising temperatures (see diagram). "There's definitely a stark contrast with the way things were at the start of the 20th century," says atmospheric scientist Leonard Druyan, of Columbia University. Recent data show the volume of Arctic sea ice has shrunk 20 percent since the 1950s; glaciers around the world are melting at rapidly increasing rates. Rivers and lakes in North America, Asia, and Europe now freeze about nine days later and thaw 10 days earlier than they did a century ago.

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Scientists tend to agree that Earth's warming climate is real. But they continue to argue over why it's happening. Some believe the trend is merely part of natural cycles in Earth's climate record--due in part to factors like the continual warming and cooling of ocean currents or changes in the sun's brightness.

But other climate experts say the major culprits of global warming have human fingerprints all over them: carbon dioxide, methane, and other waste gases spewed into the atmosphere by industry and energy (coal, gas, oil) combustion, the burning of rainforests, and car-clogged highways, among other human activities.

GAS ATTACK

Most scientists believe the only effective strategy to halt global warming is to drastically reduce emissions of powerful air pollutants like carbon dioxide ([CO.sub.2]), which accounts for two-thirds of all greenhouse, or heat-trapping, gases. In the last 150 years, the surging use of fossil fuels--coal, oil, and natural gas--has released 270 billion tons of carbon into the air in the form of carbon dioxide. Fortunately, oceans, plants, and soils absorb more than half of all atmospheric [CO.sub.2]--without them world temperatures might have already soared at an alarming rate.

One strategy to slash carbon dioxide in the air: intensive replanting of world forests. Since trees store carbon dioxide in soil and wood, replanted U.S. forests alone could absorb up to 300 million tons of carbon dioxide per year. Another radical idea: chemically remove carbon from the air and inject it into underground reservoirs or the ocean, for example--though long-term effects on the global environment are unknown.

Meanwhile, scientists now think other gases like methane, produced by natural gas and oil production, and decomposing waste in landfills, are even bigger heat-trappers than [CO.sub.2] (see p. 12). "Per molecule, methane is far more effective at trapping the sun's heat than carbon dioxide," says James Hansen, a climate researcher at NASA's Goddard Institute for Space Studies. Reducing gases like methane and nitrous oxide could regenerate cooler air and buy researchers time to develop cleaner energy sources like solar and wind power.

Although the U.S. is home to 4 percent of the world's population, it spews 25 percent of the planet's greenhouse gases into the atmosphere. The bottom line, says Hansen: "Americans must take a leadership role in reducing their own emissions--or there's little chance of avoiding a large climate change. We need to set a good example, because the rest of the world isn't going to solve the problem for us."

HOW YOU CAN HELP

* Go places by bike, scooter, or on your own two feet. If you must drive, arrange car pools to cut down on carbon dioxide emissions.

* Encourage your family to buy energy-efficient products, from cars and appliances to compact fluorescent light bulbs.

* Turn off lights, TVs, and computers when not in use.

* Help start a community tree-planting program. Trees soak up [CO.sub.2] from the air.

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Cross-Curricular Connection

Social Studies: Do further research on the major sources and producers of greenhouse gases. Then write up a set of laws that you would enact to clean up the atmosphere.

Did You Know?

* Soot and greenhouse gases combine in a complex brew in the atmosphere. Their interaction with each other and with clouds and other atmospheric ingredients are still poorly understood.

* Sea ice is currently 40 percent thinner and covers 6 percent less area than in 1980.

* Effects worldwide of global warming include: vanishing animals; spreading diseases; rising seas; melting glaciers; weather changes such as droughts, storms, floods, earlier springs, and heat waves.

Directions: Match the words in the left column with the appropriate phrases on the right.

-- 1. global warming     a. gas produced by oil and natural gas
                            production

-- 2. methane            b. Earth's rising temperatures

-- 3. greenhouse gases   c. coal, oil, and natural gas

-- 4. carbon dioxide     d. heat-trapping gases

-- 5. fossil fuels       e. gas which accounts for two thirds
                            of all greenhouse gases

ANSWERS

1. b 2. a 3. d 4. e 5. c

National Science Education Standards

Grades 5-8: transfer of energy * structure of the Earth system * understanding about science and technology

Grades 9-12: structure and properties of matter * chemical reactions * understanding about science and technology

Resources

"Debate Rises Over a Quick(er) Climate Fix," The New York Times, October 3, 2000, p. F1

"Polar Meltdown." U S. News & World Report, February 28, 2000, p. 65

"Meltdown," Time, September 4, 2000, p. 53