阅读理解.Globalwarmingistheprocessofearth'satmosphereheatingup.Overthelast100years,theaveragetemperatureofearth'satmospherehasgoneup1Fahrenheit.Theweatherhasnotchangedexactlythesamewayineveryareaofthe

　　阅读理解. Globalwarmingistheprocessofearth'satmosphereheatingup.Overthelast100years,theaverage

　　temperatureofearth'satmospherehasgoneup1Fahrenheit.Theweatherhasnotchangedexactlythe

　　samewayineveryareaoftheplanet.Butscientiststhinkthattheriseinaveragetemperatureisalready

　　affectingtheearth'sclimate.

　　Manyscientistsnowbelievethatglobalwarmingiscausedbycuttingdowntrees,producingmore

　　trash,andpollutingtheenvironmentwhicharesomeofthereasonswhythetemperaturehasgoneup.

　　Manyscientistsbelievethatthebiggestcausesofglobalwarmingarenewhumantechnologiesthat

　　releasegreenhousegasesintotheatmosphere.

　　Thegreenhouseeffectisnotnew.Certaingasesintheatmosphere,likecarbondioxide,nitrousoxide

　　andmethane,makingithardforheatenergytogointospace.Inthepast,theclimatedidn'tchangemuch

　　becausenatureproducedjusttherightamountofgreenhousegasestodealwithit.

　　Today,mostscientistsareprettysurethattherisingtemperaturecan'tbeblamedonnature.Eversince

　　theindustrialrevolutioninthe1700s,humanshavereliedonmachinesfordailylife.Andmanyofthose

　　machinesgiveoffalotofgreenhousegases.Anincreaseinthereleaseofgreenhousegasesfromhuman

　　activitiesisthrowingnatureoffbalance.

　　Theclimateisaverycomplicatedthing,butmanyscientistsagreethattherisingatmospheric

　　temperaturehasalreadydamagedtheenvironment.Sheetsofice,calledglaciers,aremeltinginAntarcticaandotherpartsoftheglobe.Asglaciersbreakoffandmeltintotheoceans,theyareaddingwarmwater

　　totheoceansandcausingthesealeveltorise.

　　Overthepast100years,thesealevelhasrisen6-8inchesaroundtheworld.Thatmeanslandalong

　　thecoastsisbeginningtodisappearunderwater.Biggerandwarmeroceansarealsoaddingtoother

　　weatherproblemscausedbypollutionintheatmosphere.Someplaceshavereceivedmorerain,others

　　havehadbiggerstormsandafewareasintheworldhaveexperiencedunusualdrou