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How to cool earth: scientists are brainstorming wild ways to combat rising temperatures. Here are six ideas. Could they really work?

Climatologists warn that the average temperature of Earth's atmosphere is rising. The culprit: a buildup of heat-trapping greenhouse gases, including carbon dioxide. Since greenhouse gases spew from smokestacks and vehicle exhausts when coal, natural gas, and oil burn, scientists recommend switching from these fossil fuels to other energy sources. But because the world isn't likely to pull the plug on fossil-fuel use anytime soon, some researchers suggest a backup plan: geoengineering, or strategies that deliberately change the climate. The unusual fixes would either remove carbon dioxide from the air or reflect sunlight back to space. Are these ideas plausible or too far-fetched? --Jacqueline Adams

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1 THE FIX: INSTALL SPACE MIRRORS

One out-of-this-world idea is to place mirrors or sunshades in space to prevent some sunlight from reaching Earth. Some researchers suggest placing the devices in orbit around Earth, while others favor the L [arrow up] point--a spot 1,500,000 kilometers (930,000 miles) away, between Earth and the sun. "It's a place where there's about as much force pulling you toward the sun as pulling you toward Earth," says Phil Rasch, a climate scientist at Pacific Northwest National Laboratory in Washington. So it is less work to keep the devices in position.

THE FACTS: Developing the needed technology could take decades and cost trillions of dollars. It wouldn't remove excess carbon dioxide from the atmosphere and the side effects are unknown, Still, it could help cool Earth in an emergency.

2 THE FIX: PLANT ARTIFICIAL TREES

Researchers at Columbia University in New York City are devising artificial trees--towers made of a material that imitates tree leaves' ability to absorb carbon dioxide. Designers say that one artificial tree could suck one ton of carbon dioxide from the atmosphere each day. Workers could then place the material in a sealed chamber, remove the carbon dioxide, and reuse the tree. The collected carbon dioxide could be sequestered, or stored, underground.

THE FACTS: The design still needs tweaking, but artificial trees could be available in a few years. One plus: The devices don't run on fossil-fuel power. The material naturally absorbs carbon dioxide from air as wind blows through it. Another plus: Artificial trees could be placed close to facilities that would pump the collected carbon dioxide underground for sequestration. Potential side effects aren't known.

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3 THE FIX: PAINT ROOFS AND ROADS WHITE

The temperature in a city is often several degrees higher than in surrounding areas. Hard, dry, and dark surfaces such as roofs and pavement soak up sunlight, causing this urban-heat-island effect. Painting these surfaces white would increase their albedo, or the percentage of sunlight they reflect. This would help cities keep their cool.

THE FACTS: Increasing a city's albedo would lower temperatures and have an added perk: Buildings would require less air conditioning, which would decrease fossil-fuel use. But since cities cover only about three percent of Earth's land surface, this technique isn't a fix-all for climate change globally. "It would have more of an effect on cooling that city area," says Warren Washington, a climate scientist at the National Center for Atmospheric Research in Colorado.

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4 THE FIX: BURY CARBON DIOXIDE

One proposal: Capture carbon dioxide from power plants, smokestacks, and vehicle exhaust pipes as it's produced. Then sequester it deep underground in places like used oil fields and coal beds. =It would essentially keep the carbon dioxide from smokestacks out of the atmosphere and bury it," says Washington, who was recently awarded the National Medal of Science by President Obama.

THE FACTS: Potential snags include concerns that the buried gas could leak out over time, or that the plan would produce more carbon dioxide. Washington explains, "You have to pump it down below the surface quite a ways, and it takes energy to pump it." This means that more fossil fuel is burned. And if the capture sites aren't near a sequestration site, then the carbon dioxide would have to be shipped in vehicles that would emit greenhouse gases. Pilot plants are testing the idea to see if the result is worth it.

5 THE FIX: WRAP GLACIERS IN FOIL

Swiss ski resorts are using a bright idea to foil climate change. To combat melting glaciers, workers spread insulating foil sheets over parts of the large ice masses during the summer. The sheets' white surface reflects sunlight, keeping the glaciers from absorbing heat.

THE FACTS: The idea seems to work--but only for the small areas the resorts can wrap. "A huge area would have to be covered to have any major effect," says Washington. Reaching glaciers in remote mountainous regions would be a tall order, and it wouldn't be a one-time trip. "You'd have to find a way to keep it clean," adds Washington. That's because once sooty air pollution darkens the sheets, they'd absorb heat rather than reflect it.

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6 THE FIX: MAKE CLOUDS BRIGHTER

Clouds that contain more or smaller water droplets have a higher albedo. The droplets form on particles in the atmosphere, called aerosols. Some scientists propose deploying wind-powered ships that would spray seawater into the air. Water droplets would form on the extra sea-salt particles, thus brightening the clouds.

THE FACTS: The idea is still on the drawing board, and scientists are using computer models to try to figure out if it would work. The problem: They don't understand enough about cloud behavior to know the exact effect this "fix" would have on the world's weather patterns. "Clouds and the way that they interact with aerosols currently are a pretty uncertain part of the climate system," says Rasch.

[VIDEO EXTRA] Watch a video about climate change at: www.scholastic.com /scienceworld

DID YOU KNOW?

* The eight warmest years on record (since 1850) have all occurred since 1998, with the warmest year being 2005.

CRITICAL THINKING:

* What can humans do to combat global warming? How do you think 21st-century life might change as we attempt to reduce our production of greenhouse gases?

PROJECT-BASED LEARNING:

ART: Pick your favorite of the featured "fixes" for global warming. Then design and construct a trifold brochure to explain your choice. Include simple, labeled drawings and bulleted information about the idea.

RESOURCES

You can access these Web links at www.scholastic.com/scienceworld.

* VIDEO EXTRA: Watch a video about climate change at: www. scholastic.com/scienceworld.

* Visit the EPA's Climate Change for Kids site for information, games, animations, and calculators: www.epa.gov/climatechange/kids.
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Title Annotation:EARTH: CLIMATE
Author:Adams, Jacqueline
Publication:Science World
Geographic Code:1USA
Date:Apr 4, 2011
Words:1078
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