Climate Change: What You Need to Know | NRDC

Natural causes of climate change ... The earth has gone through warming and cooling phases in the past, long before humans were around. Forces ... Jumptonavigation AIRSinstrumentonNASA’sAquaspacecraftshowshighcarbondioxideconcentrationsintheNorthernHemisphere. NASA/GoddardSpaceFlightCenterScientificVisualizationStudio/NASA/JPLAIRSProject JumptoSection WhatIsClimateChange? HowIsClimateChangeMeasuredOverTime? WhatCausesClimateChange? TheEffectsofGlobalClimateChange ClimateChangeFacts ClimateChangeSolutions WhatIsClimateChange? Climatechangeisgenerallydefinedasasignificantvariationofaverageweatherconditions—say,conditionsbecomingwarmer,wetter,ordrier—overseveraldecadesormore.It’sthelonger-termtrendthatdifferentiatesclimatechangefromnaturalweathervariability.Recordfloods.Ragingstorms.Deadlyheat.Climatechangemanifestsitselfinmyriadwaysandisexperiencedbyeverylivingbeing,althoughnotequally.Throughouttheworld,theeconomicallydisadvantagedandpeopleofcolor—thosewhohavecontributedtheveryleasttotherootcausesofclimatechange—arethemostlikelytosufferfromitsworstimpacts.Herearethebasicsonwhatcausesclimatechange,howit’saffectingtheplanetanditspeople,andwhatwecandoaboutit. HowIsClimateChangeMeasuredOverTime? Climatereferstothegeneralweatherconditionsofaplaceasmeasuredovermanyyears.IntheUnitedStates,forexample,Maine’sclimateiscoldandsnowyinwinterwhileSouthFlorida’sistropicalyear-round.Earth-orbitingsatellites,remotemeteorologicalstations,andoceanbuoysareusedtomonitorpresent-dayweatherandclimate,butit’spaleoclimatologydatafromnaturalsourceslikeicecores,treerings,corals,andoceanandlakesedimentsthathaveenabledscientiststoextendtheearth’sclimaticrecordsbackmillionsofyears.Theserecordsprovideacomprehensivelookatthelong-termchangesintheearth’satmosphere,oceans,landsurfaces,andcryosphere(frozenwatersystems).Scientiststhenfeedthisdataintosophisticatedclimatemodelsthatareabletopredictfutureclimatetrendswithimpressiveaccuracy. It’sworthnotingthatwhileclimatechangeandglobalwarmingareoftenusedinterchangeably,globalwarming—therecentriseintheglobalaveragetemperatureneartheearth’ssurface—isjustoneaspectofclimatechange. WhatCausesClimateChange? Themechanicsoftheearth’sclimatesystemaresimple.Whenenergyfromthesunisreflectedofftheearthandbackintospace(mostlybycloudsandice),orwhentheearth’satmospherereleasesenergy,theplanetcools.Whentheearthabsorbsthesun’senergy,orwhenatmosphericgasespreventheatreleasedbytheearthfromradiatingintospace(thegreenhouseeffect),theplanetwarms.Avarietyoffactors,bothnaturalandhuman,caninfluencetheearth’sclimatesystem. Naturalcausesofclimatechange Theearthhasgonethroughwarmingandcoolingphasesinthepast,longbeforehumanswerearound.Forcesthatcancontributetoclimatechangeincludethesun’sintensity,volcaniceruptions,andchangesinnaturallyoccurringgreenhousegasconcentrations.Butrecordsindicatethattoday’sclimaticwarming—particularlythatwhichhasoccurredsincethemid-20thcentury—ishappeningatamuchfasterratethaneverbefore,anditcan’tbeexplainedbynaturalcausesalone.AccordingtoNASA,“[t]hesenaturalcausesarestillinplaytoday,buttheirinfluenceistoosmallortheyoccurtooslowlytoexplaintherapidwarmingseeninrecentdecades.” Anthropogeniccausesofclimatechange Humans—morespecifically,thegreenhousegas(GHG)emissionsthathumanactivitygenerates—aretheleadingcauseoftheearth’srapidlychangingclimatetoday.Greenhousegasesplayanimportantroleinkeepingtheplanetwarmenoughtoinhabit.Buttheamountofthesegasesinouratmospherehasskyrocketedinrecentdecades.AccordingtotheU.S.EnvironmentalProtectionAgency,ourcurrentconcentrationsofcarbondioxide,methane,andnitrousoxide“areunprecedentedcomparedwiththepast800,000years.”Indeed,theatmosphere’sshareofcarbondioxide—theplanet’schiefclimatechangecontributor—hasrisenby46percentsincepreindustrialtimes. Awaterfrontfactorypumpingoutcloudsofsmoke Theburningoffossilfuelslikecoal,oil,andgasforelectricity,heat,andtransportationistheprimarysourceofhuman-generatedemissions.Asecondmajorsourceisdeforestation,whichreleasessequestered(orstored)carbonintotheair.It’sestimatedthatlogging,clearcutting,fires,andotherformsofforestdegradationreleaseanaverageof8.1billionmetrictonsofcarbondioxideperyear,accountingformorethan20percentofallglobalCO2emissions.Otherhumanactivitiesthatgenerateairpollutionincludefertilizeruse(aprimarysourceofnitrousoxideemissions),livestockproduction(cattle,buffalo,sheep,andgoatsaremajormethaneemitters),andcertainindustrialprocessesthatreleasefluorinatedgases.Activitieslikeagricultureandroadconstructioncanalsochangethereflectivityoftheearth’ssurface,leadingtolocalwarmingorcooling. Thoughourplanet’sforestsandoceansabsorbgreenhousegasesfromtheatmospherethroughphotosynthesisandotherprocesses,thesenaturalcarbonsinkscan’tkeepupwithourrisingemissions.Theresultingbuildupofgreenhousegasesiscausingalarminglyfastwarmingworldwide.It’sestimatedthattheearth’saveragetemperaturerosebyabout1degreeFahrenheitduringthe20thcentury.Ifthatdoesn’tsoundlikemuch,considerthis:WhenthelasticeageendedandthenortheasternUnitedStateswascoveredbymorethan3,000feetofice,averagetemperatureswerejust5to9degreescoolerthantheyarenow. TheEffectsofGlobalClimateChange AccordingtotheWorldEconomicForum’sGlobalRisksReport2021,thefailuretomitigateandadapttoclimatechangeis“themostimpactful”riskfacingcommunitiesworldwide—aheadofevenweaponsofmassdestructionandwatercrises.Blameitscascadingeffects:Asclimatechangetransformsglobalecosystems,itaffectseverythingfromtheplaceswelivetothewaterwedrinktotheairwebreathe.Andthoughclimatechangeaffectseveryoneinsomeway,it’sindisputablethatitsmostnegativeimpactsarebornedisproportionatelybycertaingroups:women,children,peopleofcolor,Indigenouscommunities,andtheeconomicallymarginalized.Climateisahumanrightsissue. Extremeweather AviewoftheSeineriverfloodinParisnearBir-Hakeimbridge,whichreacheda30-yearhighinJune2016 Shutterstock Astheearth’satmosphereheatsup,itcollects,retains,anddropsmorewater,changingweatherpatternsandmakingwetareaswetteranddryareasdrier.Highertemperaturesworsenandincreasethefrequencyofmanytypesofdisasters,includingstorms,floods,heatwaves,anddroughts.Theseeventscanhavedevastatingandcostlyconsequences,jeopardizingaccesstocleandrinkingwater,fuelingout-of-controlwildfires,damagingproperty,creatinghazardous-materialspills,pollutingtheair,andleadingtolossoflife. Dirtyair SmoginTurin,Italy MikeDotta/Shutterstock Airpollutionandclimatechangeareinextricablylinked,withoneexacerbatingtheother.Whentheearth’stemperaturesrise,notonlydoesourairgetdirtier—withsmogandsootlevelsrisingaccordingly—butitalsobecomesfilledwithmoreallergenicpollutants,suchascirculatingmold(thankstodampconditionsfromextremeweatherandmorefloods)andpollen(duetolonger,strongerpollenseasons). Healthrisks TheAedesmosquitocanspreadseriousdiseasessuchasdenguefever,yellowfever,andtheZikavirus. U.S.AirForce/MasterSgt.BrianFerguson AccordingtotheWorldHealthOrganization,“climatechangeisexpectedtocauseapproximately250,000additionaldeathsperyear”between2030and2050.Asglobaltemperaturesrise,sodothenumberoffatalitiesandillnessesfromheatstress,heatstroke,andcardiovascularandkidneydisease.Andasairpollutionworsens,sodoesrespiratoryhealth—particularlyforthe300millionpeoplelivingwithasthmaworldwide;there’smoreairbornepollenandmoldtotormenthayfeverandallergysuffererstoo.Extremeweatherevents,suchasseverestormsandflooding,canleadtoinjury,drinkingwatercontamination,andstormdamagethatmaycompromisebasicinfrastructureorleadtocommunitydisplacement.Indeed,historicalmodelssuggestthelikelihoodofbeingdisplacedbyadisasterisnow60percenthigherthanitwasfourdecadesago—andthelargestincreasesindisplacementarebeingdrivenbyweather-andclimate-relatedevents.(It’sworthnotingthatdisplacementcomeswithitsownhealththreats,suchasincreasesinurbancrowding,trauma,socialunrest,lackofcleanwater,andtransmissionofinfectiousdiseases.)Awarmer,wetterworldisalsoaboonforinsect-bornediseasessuchasdenguefever,WestNilevirus,andLymedisease. Risingseas AerialoftheMarshallIslandslandscape,whicharefeelingtheeffectsofrisingsealevels ErinMagee,DFAT TheArcticisheatinguptwiceasfastasanyotherplaceontheplanet.Asitsicesheetsmeltintotheseas,ouroceansareontracktorisebyanywherefrom0.95to3.61feetbytheendofthiscentury,threateningcoastalecosystemsandlow-lyingareas.Islandnationsfaceparticularrisk,asdosomeoftheworld’slargestcities,includingNewYorkCity,Miami,MumbaiinIndia,andSydneyinAustralia. Warmer,moreacidicoceans FishandcoralsnearLimestoneIsland,Indonesia iStock Theearth’soceansabsorbbetweenone-quarterandone-thirdofourfossilfuelemissionsandarenow30percentmoreacidicthantheywereinpreindustrialtimes.Thisacidificationposesaseriousthreattounderwaterlife,particularlycreatureswithcalcifiedshellsorskeletonslikeoysters,clams,andcoral.Itcanhaveadevastatingimpactonshellfisheries,aswellasthefish,birds,andmammalsthatdependonshellfishforsustenance.Incoastalcommunitieswherefishingandseafoodproductionsustainthelocaleconomy,thisimpactextendstohumanpopulationsaswell,destroyinglivelihoodsandopeningthedoortoeconomicruin.Risingoceantemperaturesarealsoalteringtherangeandpopulationofunderwaterspeciesandcontributingtocoralbleachingeventsthatarecapableofkillingentirereefs—ecosystemsthatsupportmorethan25percentofallmarinelife. Imperiledecosystems Twopolarbearsonasmallicefloe iStock Climatechangeisincreasingpressureonwildlifetoadapttochanginghabitats—andfast.Manyspeciesareseekingoutcoolerclimatesandhigheraltitudes,alteringseasonalbehaviors,andadjustingtraditionalmigrationpatterns.Theseshiftscanfundamentallytransformentireecosystemsandtheintricatewebsoflifethatdependonthem.Asaresult,accordingtoa2020study,one-thirdofallanimalandplantspeciescouldfaceextinctionby2070.Anotherstudyshowedthatmammals,fish,birds,reptiles,andothervertebratespeciesaredisappearingmanytimesfasterthantheyshouldbe,aphenomenonthathasbeenlinkedtoclimatechange,pollution,anddeforestation—allinterconnectedthreats.Inearly2021,climateandbiodiversityexpertsissuedajointreportillustratingtheseinterconnectionsandurgingsimultaneousactiononbothfronts.Ontheflipside,milderwintersandlongersummershaveenabledsomespeciestothrive,includingtree-killinginsectsthatareendangeringentireforests. ClimateChangeFacts Despitewhatclimatedeniersandfossilfuellackeysclaim—forinstance,thatthescienceonglobalwarmingis“farfromsettled”—there’snothingtodebate:Climatechangeisareality.InthewordsoftheIntergovernmentalPanelonClimateChange(IPCC),theforemostinternationalscientificbodyfortheassessmentofthephenomenon,“[w]armingoftheclimatesystemisunequivocal,andsincethe1950s,manyoftheobservedchangesareunprecedentedoverdecadestomillennia.Theatmosphereandoceanhavewarmed,theamountsofsnowandicehavediminished,andsealevelhasrisen.” Butyoudon’thavetobeaclimatescientisttounderstandhowtheworldhasalreadychanged.Ourlastdecade—2010to2019—washotterthananyotherdecadeinatleastthepast1,300years.Secondplacegoestothedecadebeforeit:2000to2009.Andthefirstyearofthenewdecade,2020,istiedwith2016forthehottestindividualyeareverrecorded.Withthisincreasedheat,ofcourse,havecomemorefrequentandmoreintenseweather-relateddisasters.Thefirsthalfof2021wasmarkedbyrecordheat,drought,andwildfiresinthewesternUnitedStatesandCanadaandbyrecordrainfallandfloodinginEurope.Andwithoutimmediateclimateaction,theserecordswon’tberecordsforlong:They’llbebrokennextyear,orshortlythereafter.“Thescienceisclear,”writesVijayLimaye,NRDCscientist.“Thesedangerouseffectsofclimatechangewillworseneachyearthatwefailtocurbthepollutionthatisdestabilizingourplanet.” Theresponsibilitytoreversethisworryingtrendlieswithus.Atleast97percentofactivelypublishingclimatescientistsendorsetheconsensuspositionthathumansaretheleaddriversofclimatechange.AstheIPCChasstated—withitshighestdegreeofconfidence—“Itisextremelylikelythatmorethanhalfoftheobservedincreaseinglobalaveragesurfacetemperaturefrom1951to2010wascausedbytheanthropogenicincreaseinGHGconcentrationsandotheranthropogenicforcingstogether.” UrgeBidentowithdrawU.S.fundingforinternationalfossilfuelprojects TakeAction ClimateChangeSolutions Wecanmitigateglobalclimatechangeandhelpstemitsdetrimentalimpacts,butdoingsowillrequiretacklingitsrootcause:pollutionfromburningfossilfuels.ParisAgreementTheBidenadministrationhascommittedtotheprinciplessetforthduringthe2015ParisClimateChangeConference,wherenearlyeverynationontheearthcommittedtoactionsaimedatshiftingawayfromdirtyfossilfuelsandtowardcleaner,smarterenergyoptionsinordertolimitglobaltemperaturerisethiscenturyto2degreesCelsius—or1.5degreesCelsius,ifpossible. OnEarthDayin2021,PresidentBidencommittedtheUnitedStatestocuttingitscarbonpollutionby50to52percentfrom2005levels—nearlydoublewhatPresidentObamahadpromised—andtodoitby2030,justfiveyearslaterthantheoriginaldeadlinesetwhentheUnitedStatesfirstjoinedtheagreement.Whilebold,thenewtargetsareachievable,butonlyifCongress,states,andthebusinesssectorjoinintohelpusgettherebydoingthingslikesettinganationalcleanenergystandard,electrifyingourfleetofcarsandtrucks,curbingmethaneemissions,andmaximizingbuildingefficiency. Developmentsincleanenergytechnology Everyyearbringswithitnewsofexcitingbreakthroughsintheproductionanddistributionofrenewableenergysourcessuchaswindandsolar,whicharebecomingevercheapertogenerateandevermorepopularwithconsumers,businesses,utilities,andgovernments.Atthesametime,carmakersaroundtheworldareworkingtodevelopnewbatterytechnologiesthatwillresultinthereplacementofhundredsofmillionsofgas-poweredcarswithzero-emissionsvehicles.Thesetrendsshouldbeencouragedbysmart,forward-lookingpublicpolicy—suchasBiden’sBuildBackBetteragenda,whichtiesthepost-pandemiceconomicrecoveryintheUnitedStatestoprojectsthatwillcurbclimatechangewhileputtingtensofmillionsofunemployedorunderemployedpeopletoworkingood-payingjobs. TellCongresstoheedclimatewarningsandpasstheBuildBackBetteragenda TakeAction Climateactionathome TacklingglobalclimatechangeisaHerculeantask,onethatdependsoninternationalconsensusandtheeffortsofcommunities,companies,andindividualsalike.Tothatend,manystates,fromCaliforniatoIowa,arechampioningcleanenergyindustries,suchassolarandwind;U.S.citiesaretakingactiontomitigateclimatechangeandbolsterclimateresiliencewhileplacingequityattheforefront;andcorporations—includingsomeoftheworld’slargestmultinationals—arepledgingtochangethewaytheydobusinesstoachievenet-zeroemissionsby2040. Therearemyriadwaysthatyoucanhelptoo.Youcanjoin,amplify,orotherwisesupporttheinternationalyouthclimatemovementthathasemergedinthelastfewyearsasagalvanizedresponsetogovernmentinaction;inralliesandmarchesaroundtheworld,thismovementislettingleadersknowthatdelayonclimateactionwillnolongerbetolerated.YoucanalsopickupthephonetocallCongressaboutenvironmentalpoliciesthatmatter,supportingrenewableenergyprojects,andprioritizingfuelandenergyefficiencythatwillnotonlycurbindividualcarbonemissionsbutbolstercleanalternativestodirtyfossilfuels.Wemustallstepup—andnow. ThisstorywasoriginallypublishedonFebruary23,2017,andhasbeenupdatedwithnewinformationandlinks. NRDC.orgstoriesareavailableforonlinerepublicationbynewsmediaoutletsornonprofitsundertheseconditions:Thewriter(s)mustbecreditedwithabyline;youmustnoteprominentlythatthestorywasoriginallypublishedbyNRDC.organdlinktotheoriginal;thestorycannotbeedited(beyondsimplethingssuchastimeandplaceelements,style,andgrammar);youcan’tresellthestoryinanyformorgrantrepublishingrightstootheroutlets;youcan’trepublishourmaterialwholesaleorautomatically—youneedtoselectstoriesindividually;youcan'trepublishthephotosorgraphicsonoursitewithoutspecificpermission;youshoulddropusanotetoletusknowwhenyou’veusedoneofourstories. RelatedStories LatestNews Here’sWhat’sHappeningatCOP26 We’rekeepingtrackofthelatestnewsfromGlasgowasgovernmentandclimateleadershashouthowtoreininrunawaywarming. Explainer WillCOP26MoveUsClosertoSolvingtheClimateCrisis? Leadersfromacrosstheglobewillmeetsoontoaccelerateactionstoconfrontclimatechange.Here’swhattoexpect. 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