Meltingicebergs inEriksfjord,Greenland.

V\fARM||MMany scientists agree that Earth's climat̂ ^has warmed in recent years. But ndt all 6^'them think it is a cause for concerjv " \^

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by Sean McCollum

If you want to see the glaciers (huge masses of ice) that gaveGlacier National Park its name, don't wait too long. When PresidentWilliam Howard Taft made the Montana area a national park in

1910, there were about 150 of the massive ice forms. That number hassince melted away fo around 20.

"The ones that remain areshrinking," says Dan Fagre (FAY-gree), a scientist with the U.S.Geological Survey. "We're literallywatching glaciers disappear beforeour eyes." Fagre predicts thatmost, if not all, ofthe park'sremaining glaciers will be gonewithin 30 years.

Scientists around the world agreethat our planet is getting warmer.Flowers bloom earlier in the spring.

Warm-weather plants, insects,birds, and other animals are migrat-ing to once-cooler regions. Averageglobal temperatures have risen overthe last 50 years. And, scientists say,the thick ice cap covering theNorth Pole is melting.

"It's here. It's real," says TimBarnett about global warming.Barnett is a climatologist at theScripps Institution of Oceanogra-phy in California. "Among [most]

scientists, there's no question thatthis is what's happening—and it'sgoing to affect every single personon Earth."

The Greenhouse EffectOver millions of years. Earth's

climate has shifted betweenwarmer and cooler temperaturesmany, many times. Is the current

Words to Know• climatologist: a scientist who studies

Earth's long-term climate as well astrends and changes that may affect it.

• emission: something discharged orsent into the air.

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warming trend part of this naturalcycle, or something more?

Many scientists think that it issomething more. At least patt ofthewarming, they say, is due to pollu-tion created by humans. Commonactivities, such as burning fossilfuels—oil, gas, and coal—give offcarbon dioxide (CO2) and othergases. Most ofthe burning resultsfrom cars, factories, and the powerplants that provide energy for housesand office buildings. These gases stayin the atmosphere, intensifyingEarths natural "greenhouse effect."

What is the greenhouse effect?Imagine the inside ofa cat on asunny day. Sunlight comes inthrough the windows (as it doesthrough Earths atmosphere). Thelight gets trapped inside the car,heating the interior. If a window isopen, some ofthe heat escapes, butit still remains warm inside the car.If all the windows are shut, however,the heat builds up. The seats and theair inside the car get much hotter.

Earth's atmosphere naturallycreates a greenhouse effect, whichis what helps make life on Earthpossible. Without the atmosphere.

much ofthe sun's energy wouldbounce back into space, and Earth'ssurface would be too cold to sup-port life. But many chmatologiststhink that gases from humanpollution are, in effect, closing tbewindows. As more heat energy istrapped inside the atmosphere,global temperatures rise.

Scientists have found that therise in global temperatures matchesthe rise in CO2 levels in Earth'satmosphere. There may already beenough CO2 in the atmosphere tokeep warming the planet fordecades to come. Computermodels predict that Earth's tem-peratures may rise an additional2.5 to 10.4 degrees Fahrenheit inthe next 100 years.

Should We Worry?If Earth really is getting warmer,

should we be concerned? Mostexperts agree that human activity isaffecting global temperatures. Butthey are split about whether thisposes a serious threat.

John Christy, director oftheEarth System Science Center at theUniversity of Alabama at Huntsville,

believes that the projected rise intemperatures will not be dramaticenough to cause serious problems."Most ofthe predictions are tooalarmist," he says.

Patrick J. Michaels, a climatolo-gist for the state of Virginia, agrees."The fact ofthe matter is," he says,"if you look at those temperaturerecords that [people] keep on cit-ing, you will see that almost all ofthe warming takes place in theabsolute coldest, most miserable airmasses in Siberia and northwestern

North America We've warmedSiberia from minus 40 [degreesFahrenheit] to minus 38. Big deal."

Other experts, however, say thatit is a big deal. Global tempera-tures just a few degrees warmercould alter weather patterns andsea levels, and lead to flooding,drought, a rise in tbe number ofdamaging storms, and the spreadof mosquito-borne diseases.

Glacial melt raises another con-cern. Much ofthe world's popula-tion relies on glaciers for water todrink and to irrigate crops. "Inplaces like tbe Himalayas [a moun-tain range in Asia], the summer

warmer could alter weather patternsand sea levels, and lead to flooding, drought,a rise in the number of damaging storms,and the spread of mosquito-borne diseases.

Prolonged drought hasdried up much of Utah's

Lake Powell, once one ofthe largest artificially

created lakes in the world.

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Caili5e and EffectCarbon Emissions Average Earth

Temperature,at Surface

1970 1980 1990 20A R S

1920Y E A R S

A factory pollutes the air in Antwerp, Belgium.

water supply is 100 percent glaciermeltwater," says Fagre. "But thoseglaciers may be gone by 2030."

The Neto York Times reported onanother disturbing trend in January.Scientists in Antarctica have foundthat rising temperatures in some areasthere have caused glaciers to thin andice shelves the size of some U.S. statesto disintegrate or recede. On theAntarctic Peninsula, grass is appear-ing in places that were once hiddenunder a blanket of ice and snow.

"The evidence is piling up; every-thing fits," Robert Thomas, aglaciologist from NASA, told theTimes. 'Around the Amundsen Sea,we have surveyed a half dozen gla-ciers. All are thinning, in some casesquite rapidly, and in each case, theice shelf is also thinning."

What are the implications ofthis? If enough glaciers, which reston land, slide into the sea, theincrease in ocean volume could raisethe global sea level.

"If Antarctica collapses, it willhave a major effect on the wholeglobe," said Eric Rignot, a glaciolo-gist at NASA's Jet PropulsionLaboratory in Pasadena, California.

Kyoto ProtocolMany scientists, as well as world

leaders, believe that we should takeimmediate steps to reduce green-house-gas emissions. Buildingcleaner power plants, driving carsthat pollute less, and developing newfuels are some proposals for doingso. About 120 countries have signedan international agreement calledthe Kyoto Protocol. After years ofnegotiations, the treaty took effecton February 16, 2005. It calls forcountries to take immediate steps toreduce the release of C O T and fiveother gases into the atmosphere.

The United States participatedin early negotiations on the treaty,but President George W. Bushordered a withdrawal from the

talks in 2001. Since the agreementdoes not place restrictions ondeveloping countries, the Presidentargued, it puts undue pressure onindustrialized nations. Australiahas also refused to ratify (approve)the treaty.

The debate about global warm-ing is likely to continue as yourgeneration comes of age. Today'skids, says Tim Barnett, "shouldlearn about the climate and howit's changing. They should have asay about the world they're goingto inherit." JS

THINK ABOUT IT1. What are some exannples offossil fuels?2. Oo you think that global warm-ing is something to worry aboutnow, sometime in the future, ornot at all? Explain.

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