阅读理解。
Globalwarmingistheprocessofearth'satmosphereheatingup.Overthelast100yearstheaverage
temperatureofearth'satmospherehasgoneup1Fahrenheit.Theweatherhasnotchangedexactlythe
samewayineveryareaoftheplanet.Butscientiststhinkthattheriseinaveragetemperatureisalready
affectingtheearth'sclimate.
Manyscientistsnowbelievethatglobalwarmingiscausedbycuttingdowntreesproducingmore
trashandpollutingtheenvironmentwhicharesomeofthereasonswhythetemperaturehasgoneup.
Manyscientistsbelievethatthebiggestcausesofglobalwarmingarenewhumantechnologiesthat
releasegreenhousegasesintotheatmosphere.
Thegreenhouseeffectisnotnew.Certaingasesintheatmospherelikecarbondioxidenitrousoxide
andmethanemakingithardforheatenergytogointospace.Inthepasttheclimatedidn'tchangemuch
becausenatureproducedjusttherightamountofgreenhousegasestodealwithit.
Todaymostscientistsareprettysurethattherisingtemperaturecan'tbeblamedonnature.Eversince
theindustrialrevolutioninthe1700shumanshavereliedonmachinesfordailylife.Andmanyofthose
machinesgiveoffalotofgreenhousegases.Anincreaseinthereleaseofgreenhousegasesfromhuman
activitiesisthrowingnatureoffbalance.
Theclimateisaverycomplicatedthingbutmanyscientistsagreethattherisingatmospheric
temperaturehasalreadydamagedtheenvironment.SheetsoficecalledglaciersaremeltinginAntarcticaandotherpartsoftheglobe.Asglaciersbreakoffandmeltintotheoceanstheyareaddingwarmwater
totheoceansandcausingthesealeveltorise.
Overthepast100yearsthesealevelhasrisen6-8inchesaroundtheworld.Thatmeanslandalong
thecoastsisbeginningtodisappearunderwater.Biggerandwarmeroceansarealsoaddingtoother
weatherproblemscausedbypollutionintheatmosphere.Someplaceshavereceivedmorerainothers
havehadbiggerstormsandafewareasintheworldhaveexperiencedunusualdroughts.
1.Whatismainlytalkedaboutinthispassage?
A
