Download global warming - National Geographic Society

Thiswebsitewouldliketoremindyou:Yourbrowser(AppleSafari4)isoutofdate.Updateyourbrowserformore
security,comfortandthebestexperienceonthissite.
×
EncyclopedicEntry
globalwarming
Forthecompleteencyclopedicentrywithmediaresources,visit:
http://education.nationalgeographic.com/encyclopedia/global-warming/
GlobalwarmingdescribesthecurrentriseintheaveragetemperatureofEarth’sairandoceans.Globalwarmingis
oftendescribedasthemostrecentexampleofclimatechange.
Earth’sclimatehaschangedmanytimes.Ourplanethasgonethroughmultipleiceages,inwhichicesheetsand
glacierscoveredlargeportionsoftheEarth.Ithasalsogonethroughwarmperiodswhentemperatureswere
higherthantheyaretoday.
PastchangesinEarth’stemperaturehappenedveryslowly,overhundredsofthousandsofyears.However,the
recentwarmingtrendishappeningmuchfasterthaniteverhas.Naturalcyclesofwarmingandcoolingarenot
enoughtoexplaintheamountofwarmingwehaveexperiencedinsuchashorttime—onlyhumanactivitiescan
accountforit.Scientistsworrythattheclimateischangingfasterthansomelivingthingscanadapttoit.
In1988,theWorldMeteorologicalOrganizationandtheUnitedNationsEnvironmentProgrammeestablisheda
committeeofclimatologists,meteorologists,geographers,andotherscientistsfromaroundtheworld.This
IntergovernmentalPanelonClimateChange(IPCC)includesthousandsofscientistswhoreviewthemostup-todateresearchavailablerelatedtoglobalwarmingandclimatechange.TheIPCCevaluatestheriskofclimate
changecausedbyhumanactivities.
AccordingtotheIPCC’smostrecentreport(in2007),Earth’saveragesurfacetemperatureshaverisenabout0.74
degreesCelsius(1.33degreesFahrenheit)duringthepast100years.Theincreaseisgreaterinnorthern
latitudes.TheIPCCalsofoundthatlandregionsarewarmingfasterthanoceans.TheIPCCstatesthatmostofthe
temperatureincreasesincethemid-20thcenturyislikelyduetohumanactivities.
TheGreenhouseEffect
Humanactivitiescontributetoglobalwarmingbyincreasingthegreenhouseeffect.Thegreenhouseeffect
happenswhencertaingases—knownasgreenhousegases—collectinEarth’satmosphere.Thesegases,which
occurnaturallyintheatmosphere,includecarbondioxide,methane,nitrogenoxide,andfluorinatedgases
sometimesknownaschlorofluorocarbons(CFCs).
Greenhousegasesletthesun’slightshineontotheEarth’ssurface,buttheytraptheheatthatreflectsbackupinto
theatmosphere.Inthisway,theyactliketheinsulatingglasswallsofagreenhouse.Thegreenhouseeffectkeeps
Earth’sclimatecomfortable.Withoutit,surfacetemperatureswouldbecoolerbyabout33degreesCelsius(60
degreesFahrenheit),andmanylifeformswouldfreeze.
SincetheIndustrialRevolutioninthelate1700sandearly1800s,peoplehavebeenreleasinglargequantitiesof
greenhousegasesintotheatmosphere.Thatamounthasskyrocketedinthepastcentury.Greenhousegas
1of9
emissionsincreased70percentbetween1970and2004.Emissionsofcarbondioxide,themostimportant
greenhousegas,rosebyabout80percentduringthattime.Theamountofcarbondioxideintheatmosphere
todayfarexceedsthenaturalrangeseenoverthelast650,000years.
Mostofthecarbondioxidethatpeopleputintotheatmospherecomesfromburningfossilfuelssuchasoil,coal,
andnaturalgas.Cars,trucks,trains,andplanesallburnfossilfuels.Manyelectricpowerplantsalsoburnfossil
fuels.
Anotherwaypeoplereleasecarbondioxideintotheatmosphereisbycuttingdownforests.Thishappensfortwo
reasons.Decayingplantmaterial,includingtrees,releasestonsofcarbondioxideintotheatmosphere.Livingtrees
absorbcarbondioxide.Bydiminishingthenumberoftreestoabsorbcarbondioxide,thegasremainsinthe
atmosphere.
Mostmethaneintheatmospherecomesfromlivestockfarming,landfills,andfossilfuelproductionsuchascoal
miningandnaturalgasprocessing.Nitrousoxidecomesfromagriculturaltechnologyandfossilfuelburning.
Fluorinatedgasesincludechlorofluorocarbons,hydrochlorofluorocarbons,andhydrofluorocarbons.These
greenhousegasesareusedinaerosolcansandrefrigeration.
Allofthesehumanactivitiesaddgreenhousegasestotheatmosphere,trappingmoreheatthanusualand
contributingtoglobalwarming.
EffectsofGlobalWarming
Evenslightrisesinaverageglobaltemperaturescanhavehugeeffects.Perhapsthebiggest,mostobviouseffect
isthatglaciersandicecapsmeltfasterthanusual.Themeltwaterdrainsintotheoceans,causingsealevelstorise
andoceanstobecomelesssalty.
Icesheetsandglaciersadvanceandretreatnaturally.AsEarth’stemperaturehaschanged,theicesheetshave
grownandshrunk,andsealevelshavefallenandrisen.AncientcoralsfoundonlandinFlorida,Bermuda,andthe
Bahamasshowthatthesealevelmusthavebeen5to6meters(16-20feet)higher130,000yearsagothanitis
today.Earthdoesn’tneedtobecomeoven-hottomelttheglaciers.Northernsummerswerejust3to5degrees
Celsius(5-9degreesFahrenheit)warmerduringthetimeofthoseancientfossilsthantheyaretoday.
However,thespeedatwhichglobalwarmingistakingplaceisunprecedented.Theeffectsareunknown.
Glaciersandicecapscoverabout10percentoftheworld’slandmasstoday.Theyholdabout75percentofthe
world’sfreshwater.Ifallofthisicemelted,sealevelswouldrisebyabout70meters(230feet).TheIPCCreported
thattheglobalsealevelroseabout1.8millimeters(0.07inches)peryearfrom1961to1993,and3.1millimeters
(0.12inches)peryearsince1993.
Risingsealevelscouldfloodcoastalcommunities,displacingmillionsofpeopleinareassuchasBangladesh,the
Netherlands,andtheU.S.stateofFlorida.Forcedmigrationwouldimpactnotonlythoseareas,buttheregionsto
whichthe“climaterefugees”flee.MillionsmorepeopleincountrieslikeBolivia,Peru,andIndiadependonglacial
meltwaterfordrinking,irrigation,andhydroelectricpower.Rapidlossoftheseglacierswoulddevastatethose
countries.
Glacialmelthasalreadyraisedtheglobalsealevelslightly.However,scientistsarediscoveringwaysthesealevel
couldincreaseevenfaster.Forexample,themeltingoftheChacaltayaGlacierinBoliviahasexposeddarkrocks
beneathit.Therocksabsorbheatfromthesun,speedingupthemeltingprocess.
2of9
Manyscientistsusetheterm“climatechange”insteadof“globalwarming.”Thisisbecausegreenhousegas
emissionsaffectmorethanjusttemperature.Anothereffectinvolveschangesinprecipitationlikerainandsnow.
Patternsinprecipitationmaychangeorbecomemoreextreme.Overthecourseofthe20thcentury,precipitation
increasedineasternpartsofNorthandSouthAmerica,northernEurope,andnorthernandcentralAsia.However,
ithasdecreasedinpartsofAfrica,theMediterranean,andpartsofsouthernAsia.
FutureChanges
Nobodycanlookintoacrystalballandpredictthefuturewithcertainty.However,scientistscanmakeestimates
aboutfuturepopulationgrowth,greenhousegasemissions,andotherfactorsthataffectclimate.Theycanenter
thoseestimatesintocomputermodelstofindoutthemostlikelyeffectsofglobalwarming.
TheIPCCpredictsthatgreenhousegasemissionswillcontinuetoincreaseoverthenextfewdecades.Asaresult,
theypredicttheaverageglobaltemperaturewillincreasebyabout0.2degreesCelsius(0.36degreesFahrenheit)
perdecade.Evenifwereducegreenhousegasandaerosolemissionstotheir2000levels,wecanstillexpecta
warmingofabout0.1degreeCelsius(0.18degreesFahrenheit)perdecade.
Thepanelalsopredictsglobalwarmingwillcontributetosomeseriouschangesinwatersuppliesaroundtheworld.
Bythemiddleofthe21stcentury,theIPCCpredicts,riverrunoffandwateravailabilitywillmostlikelyincreaseat
highlatitudesandinsometropicalareas.However,manydryregionsinthemid-latitudesandtropicswill
experienceadecreaseinwaterresources.
Asaresult,millionsofpeoplemaybeexposedtowatershortages.Watershortagesdecreasetheamountofwater
availablefordrinking,electricity,andhygiene.Shortagesalsoreducewaterusedforirrigation.Agriculturaloutput
wouldslowandfoodpriceswouldclimb.ConsistentyearsofdroughtintheGreatPlainsoftheUnitedStatesand
Canadawouldhavethiseffect.
IPCCdataalsosuggestthatthefrequencyofheatwavesandextremeprecipitationwillincrease.Weatherpatterns
suchasstormsandtropicalcycloneswillbecomemoreintense.Stormsthemselvesmaybestronger,more
frequent,andlonger-lasting.Theywouldbefollowedbystrongerstormsurges,theimmediateriseinsealevel
followingstorms.Stormsurgesareparticularlydamagingtocoastalareasbecausetheireffects(flooding,erosion,
damagetobuildingsandcrops)arelasting.
WhatWeCanDo
Reducingourgreenhousegasemissionsisacriticalstepinslowingtheglobalwarmingtrend.Manygovernments
aroundtheworldareworkingtowardthisgoal.
ThebiggesteffortsofarhasbeentheKyotoProtocol,whichwasadoptedin1997andwentintoeffectin2005.By
theendof2009,187countrieshadsignedandratifiedtheagreement.Undertheprotocol,37industrialized
countriesandtheEuropeanUnionhavecommittedtoreducingtheirgreenhousegasemissions.
Thereareseveralwaysthatgovernments,industries,andindividualscanreducegreenhousegases.Wecan
improveenergyefficiencyinhomesandbusinesses.Wecanimprovethefuelefficiencyofcarsandothervehicles.
Wecanalsosupportdevelopmentofalternativeenergysources,suchassolarpowerandbiofuels,thatdon’t
involveburningfossilfuels.
Somescientistsareworkingtocapturecarbondioxideandstoreitunderground,ratherthanletitgointothe
atmosphere.Thisprocessiscalledcarbonsequestration.
3of9
Treesandotherplantsabsorbcarbondioxideastheygrow.Protectingexistingforestsandplantingnewonescan
helpbalancegreenhousegasesintheatmosphere.
Changesinfarmingpracticescouldalsoreducegreenhousegasemissions.Forexample,farmsuselarge
amountsofnitrogen-basedfertilizers,whichincreasenitrogenoxideemissionsfromthesoil.Reducingtheuseof
thesefertilizerswouldreducetheamountofthisgreenhousegasintheatmosphere.
Thewayfarmershandleanimalmanurecanalsohaveaneffectonglobalwarming.Whenmanureisstoredas
liquidorslurryinpondsortanks,itreleasesmethane.Whenitdriesasasolid,however,itdoesnot.
Reducinggreenhousegasemissionsisvitallyimportant.However,theglobaltemperaturehasalreadychanged
andwillmostlikelycontinuetochangeforyearstocome.TheIPCCsuggeststhatpeopleexplorewaystoadaptto
globalwarmingaswellastrytosloworstopit.Someofthesuggestionsforadaptinginclude:
Expandingwatersuppliesthroughraincatchment,conservation,reuse,anddesalination.
Adjustingcroplocations,variety,andplantingdates.
Buildingseawallsandstormsurgebarriersandcreatingmarshesandwetlandsasbuffersagainstrisingsealevels.
Creatingheat-healthactionplans,boostingemergencymedicalservices,andimprovingdiseasesurveillanceandcontrol.
Diversifyingtourismattractions,becauseexistingattractionslikeskiresortsandcoralreefsmaydisappear.
Planningforroadsandraillinestocopewithwarmingand/orflooding.
Strengtheningenergyinfrastructure,improvingenergyefficiency,andreducingdependenceonsinglesourcesofenergy.
VOCABULARY
Term
PartofSpeech
Definition
abnormal
adjective
unusual.
adapt
verb
toadjusttonewsurroundingsoranewsituation.
aerosolcan
noun
containerofliquidmaterialunderhighpressure.Whenreleasedthrough
asmallopening,theliquidbecomesasprayorfoam.
agriculturaltechnology
noun
theartandscienceofcomplexmachinesusedtoperformtasks
associatedwithfarmingandranching.
ancient
adjective
veryold.
atmosphere
noun
layersofgasessurroundingaplanetorothercelestialbody.
biofuel
noun
energysourcederiveddirectlyfromorganicmatter,suchasplants.
buffer
noun
acushionorshield.
carbondioxide
noun
greenhousegasproducedbyanimalsduringrespirationandusedby
plantsduringphotosynthesis.Carbondioxideisalsothebyproductof
burningfossilfuels.
carbonicacid
noun
chemicalproducedascarbondioxidedissolvesinwater.
carbonsequestration
noun
processofcapturingcarbonemissionsandstoringthemunderground.
century
noun
100years.
chlorofluorocarbon
(CFC)
noun
chemicalcompoundmostlyusedinrefrigerantsandflame-retardants.
SomeCFCshavedestructiveeffectsontheozonelayer.
climate
noun
allweatherconditionsforagivenlocationoveraperiodoftime.
4of9
climatechange
noun
gradualchangesinalltheinterconnectedweatherelementsonour
planet.
climaterefugee
noun
personforcedtoleavehisorherhomeandcommunitybecauseof
climatechange.
climatologist
noun
personwhostudieslong-termpatternsinweather.
coal
noun
dark,solidfossilfuelminedfromtheearth.
coast
noun
edgeoflandalongtheseaorotherlargebodyofwater.
committee
noun
groupofpeopleelectedorappointedtoperformatask.
conservation
noun
managementofanaturalresourcetopreventexploitation,destruction,or
neglect.
consistent
adjective
maintainingasteady,reliablequality.
cope
verb
tohandleordealwithproblems.
coral
noun
tinyoceananimal,someofwhichsecretecalciumcarbonatetoformreefs.
coralreef
noun
rockyoceanfeaturesmadeupofmillionsofcoralskeletons.
critical
adjective
veryimportant.
cyclone
noun
weathersystemthatrotatesaroundacenteroflowpressureandincludes
thunderstormsandrain.Usually,hurricanesrefertocyclonesthatform
overtheAtlanticOcean.
data
pluralnoun
(singular:datum)informationcollectedduringascientificstudy.
decade
noun
10years.
decay
verb
torotordecompose.
desalination
noun
processofconvertingseawatertofreshwaterbyremovingsaltand
minerals.
devastate
verb
todestroy.
diminish
verb
tobecomesmallerorlessimportant.
dissolve
verb
tobreakupordisintegrate.
diverse
adjective
variedorhavingmanydifferenttypes.
drought
noun
periodofgreatlyreducedprecipitation.
electricity
noun
setofphysicalphenomenaassociatedwiththepresenceandflowof
electriccharge.
emission
noun
dischargeorrelease.
encore
noun
reappearancebyaperformeraftertheendoftheperformance.
energyefficiency
noun
useofarelativelysmallamountofenergyforagiventask,purpose,or
service;achievingaspecificoutputwithlessenergyinput.
erosion
noun
actinwhichearthiswornaway,oftenbywater,wind,orice.
establish
verb
toformorofficiallyorganize.
5of9
EuropeanUnion
noun
associationofEuropeannationspromotingfreetrade,easeof
transportation,andculturalandpoliticallinks.
evaluate
verb
todecidesomething'sworth.
farming
noun
theart,science,andbusinessofcultivatingthelandforgrowingcrops.
fertilizer
noun
nutrient-richchemicalsubstance(naturalormanmade)appliedtosoilto
encourageplantgrowth.
flee
verb
torunaway.
fluorinate
verb
toaddorcombinewiththeelementfluorine(F).
forest
noun
ecosystemfilledwithtreesandunderbrush.
fossil
noun
remnant,impression,ortraceofanancientorganism.
fossilfuel
noun
coal,oil,ornaturalgas.Fossilfuelsformedfromtheremainsofancient
plantsandanimals.
freeze
noun
weatherpatternoftemperaturesbelow0degreesCelsius(32degrees
Fahrenheit).
fuelefficiency
noun
abilitytoproduceasmuchpowerwithaslittlefuelconsumedaspossible.
geographer
noun
personwhostudiesplacesandtherelationshipsbetweenpeopleand
theirenvironments.
glacier
noun
massoficethatmovesslowlyoverland.
globalwarming
noun
increaseintheaveragetemperatureoftheEarth'sairandoceans.
GreatPlains
noun
grasslandregionofNorthAmerica,betweentheRockyMountainsand
theMississippiRiver.
greenhouse
noun
building,oftenmadeofglassorotherclearmaterial,usedtohelpplants
grow.
greenhouseeffect
noun
phenomenonwheregasesallowsunlighttoenterEarth'satmospherebut
makeitdifficultforheattoescape.
greenhousegas
noun
gasintheatmosphere,suchascarbondioxide,methane,watervapor,
andozone,thatabsorbssolarheatreflectedbythesurfaceoftheEarth,
warmingtheatmosphere.
heat-healthactionplan
noun
publicsystemforpreventingorreducingdeathanddiseasedueto
extremeheatwaves.
heatwave
noun
periodofunusuallyhotweather.
hydrochlorofluorocarbon
noun
greenhousegasoftenusedasanindustrialcoolingmaterial.
hydroelectricpower
noun
usableenergygeneratedbymovingwaterconvertedtoelectricity.
hygiene
noun
scienceandmethodsofkeepingcleanandhealthy.
iceage
noun
longperiodofcoldclimatewhereglacierscoverlargepartsoftheEarth.
Thelasticeagepeakedabout20,000yearsago.Alsocalledglacialage.
icecap
noun
areaoffewerthan50,000squarekilometers(19,000squaremiles)
coveredbyice.
icesheet
noun
thicklayerofglacialicethatcoversalargeareaofland.
6of9
industrialization
noun
growthofmachineproductionandfactories.
IndustrialRevolution
noun
changeineconomicandsocialactivities,beginninginthe18thcentury,
broughtbythereplacementofhandtoolswithmachineryandmass
production.
infrastructure
noun
structuresandfacilitiesnecessaryforthefunctioningofasociety,suchas
roads.
insect
noun
typeofanimalthatbreathesairandhasabodydividedintothree
segments,withsixlegsandusuallywings.
IntergovernmentalPanel
onClimateChange
(IPCC)
noun
groupofscientistswhoreviewthemostup-to-dateresearchavailable
relatedtoglobalwarmingandclimatechange.
irrigation
noun
wateringland,usuallyforagriculture,byartificialmeans.
KyotoProtocol
noun
(1997)internationalagreementtoreducegreenhousegasemissions.
landfill
noun
sitewheregarbageislayeredwithdirtandotherabsorbingmaterialto
preventcontaminationofthesurroundinglandorwater.
landmass
noun
largeareaofland.
latitude
noun
distancenorthorsouthoftheEquator,measuredindegrees.
livestock
animalsraisedforsaleandprofit.
manure
noun,plural
noun
noun
marsh
noun
wetlandareausuallycoveredbyashallowlayerofseawateror
freshwater.
meltwater
noun
freshwaterthatcomesfrommeltingsnoworice.
meteorologist
noun
personwhostudiespatternsandchangesinEarth'satmosphere.
methane
noun
chemicalcompoundthatisthebasicingredientofnaturalgas.
migration
noun
movementofagroupofpeopleoranimalsfromoneplacetoanother.
model
noun
imageorimpressionofanobjectusedtorepresenttheobjectorsystem.
multiple
adjective
many.
naturalgas
noun
typeoffossilfuelmadeupmostlyofthegasmethane.
nitrogen
noun
chemicalelementwiththesymbolN,whosegasformis78%ofthe
Earth'satmosphere.
nitrousoxide
noun
greenhousegasusedinmedicineandthemanufactureofrockets.Also
knownaslaughinggasorhappygas.
oil
noun
fossilfuelformedfromtheremainsofmarineplantsandanimals.Also
knownaspetroleumorcrudeoil.
penguin
noun
birdnativetotheAntarctic.
powerplant
noun
industrialfacilityforthegenerationofelectricenergy.
precipitation
noun
allformsinwhichwaterfallstoEarthfromtheatmosphere.
protocol
noun
seriesofrules.
animalexcrementorwasteusedtofertilizesoil.
7of9
raincatchment
noun
systemtocollectandstorerainwater.
ratify
verb
toformallyapproveorconfirm.
refrigerant
noun
substanceusedtokeepmaterialscool.
research
noun
scientificobservationsandinvestigationintoasubject,usuallyfollowing
thescientificmethod:observation,hypothesis,prediction,
experimentation,analysis,andconclusion.
runoff
noun
overflowoffluidfromafarmorindustrialfactory.
sealevel
noun
baselevelformeasuringelevations.Sealevelisdeterminedby
measurementstakenovera19-yearcycle.
seawall
noun
barrierbuilttoprotectabeachorshorelinefromerosion.Alsocalleda
bulkhead.
skiresort
noun
facilitywherepeoplecanskiforrecreationorsport.
skyrocket
verb
toincreaserapidly.
slurry
noun
liquidwaste,suchasthatfromthecoalminingandcleaningprocess,also
calledsludge.
snow
noun
precipitationmadeoficecrystals.
solarpower
noun
rateofproducing,transferring,orusingsolarenergy.
spruce
noun
coniferous,orcone-bearing,tree.
storm
noun
severeweatherindicatingadisturbedstateoftheatmosphereresulting
fromupliftedair.
stormsurge
noun
abnormalriseinsealevelaccompanyingahurricaneorotherintense
storm.Alsocalledastormtide.
stormsurgebarrier
noun
wallsorobstaclesbuilttopreventoceanorriverwaterfromflowinginto
anareaafterastorm.Alsocalledleveeorfloodgate.
surveillance
noun
observationofaperson,community,orsituation.
temperature
noun
degreeofhotnessorcoldnessmeasuredbyathermometerwitha
numericalscale.
tourism
noun
theindustry(includingfood,hotels,andentertainment)oftravelingfor
pleasure.
tropical
adjective
existinginthetropics,thelatitudesbetweentheTropicofCancerinthe
northandtheTropicofCapricorninthesouth.
UnitedNations
Environment
Programme
noun
organizationwhosemissionistoprovideinternationalleadershipand
encouragepartnershipsincaringfortheenvironment.
unprecedented
adjective
neverbeforeknownorexperienced.
vital
adjective
necessaryorveryimportant.
watershortage
noun
reductionintheamountoffreshwateravailablefordrinking,hygiene,and
industrialandagriculturaluse.
8of9
watersupply
noun
amountofavailablefreshwaterfordrinking,hygiene,andindustrialand
agriculturaluse.
weatherpattern
noun
repeatingorpredictablechangesintheEarth'satmosphere,suchas
winds,precipitation,andtemperatures.
wetland
noun
areaoflandcoveredbyshallowwaterorsaturatedbywater.
WorldMeteorological
Organization
noun
UnitedNationsagencythatstudiestheEarth'satmosphere,itsinteraction
withtheoceans,theclimate,andthedistributionofwaterresources.
ForFurtherExploration
Audio&Video
NationalGeographicVideo:GlobalWarming101
Images
FoodandAgricultureOrganization:FactFile—GlobalWarming
Worksheets&Handouts
UnitedNationsEnvironmentProgramme:ClimateChangeToolkit
Websites
NationalGeographicEnvironment:GlobalWarming
©1996–2015NationalGeographicSociety.Allrightsreserved.
9of9