Geo notes(LORMS)

1 Causesofclimatechange(naturalandhuman) Naturalcauses(ChangesintheEarth’sorbitandangleoftilt,sunspotoccurrences,large-scalevolcaniceruptions) Humancauses(Burningoffossilfuels,changinglanduse) —————————————————————————————————————————- Naturalcauses: ChangesintheEarth’sorbit:TheEarth’sorbitshiftsfromcirculartoellipticalandback.Whenmostelliptical,Earthtravelsinanovalpath,receivingmoresolarradiationatitsclosestapproachthanatitsfarthestpoint.Forexample,Earth’sorbitshiftsfromcirculartoellipticalevery100,000years,affectingseasonalsolarenergylevels. Earthtilt:TheEarth’saxistiltsbetween21.5ºand24.5º.Whentiltdecreases,hemispheresleanfurtherfromtheSun,causingwarmerwinters,coolersummers,andallowingicesheetstobuild,coolingtheEarth.Forexample,theEarth’stiltchangesevery41,000years. Sunspotoccurrences:Highersunspotactivityislinkedtoincreasedsolarradiation.Thoughsunspotsarecooler,areasaroundthememitmoreenergy,raisingEarth’stemperatures.PeriodsofmaximumsunspotsgenerallyalignwithwarmersurfacetemperaturesonEarth,followingan11-yearcycle. Large-scalevolcaniceruptions:Volcaniceruptionsreleasecarbondioxide,watervapor,sulfurdioxide,dust,andashintotheatmosphere.Sulfur-basedparticles,dust,andashspread,reflectingsolarenergybackintospace,temporarilycoolingEarth.Forexample,MountPinatubo’s1991eruptionloweredglobaltemperaturesby0.6°Cfor15months. —————————————————————————————————————————- Humancauses: Burningfossilfuels:Fossilfuels,richincarbon,releasecarbondioxideandothergreenhousegaseswhenburned,enhancingthegreenhouseeffect.Theypoweractivitieslikeagriculture,industry,andurbanization.Sincethe1880sindustrialrevolution,fossilfuelusehassurged,nowcontributingover35billiontonnesofcarbondioxideemissionsyearly. Changinglanduse Deforestation:Large-scaledeforestationforagriculture,industry,andurbanizationenhancesthegreenhouseeffect.Forestsareclearedforresources(timber)andlanduse,reducingcarbondioxideabsorptionbytrees.Cuttingorburningtreesreleasesstoredcarbon,whileexposedsoilincreasescarbondioxidethroughoxidation.Forexample,tropicaldeforestationcontributesroughly20%ofglobalgreenhousegasemissions. Agriculture:Aspopulationsgrow,forestsareclearedforagriculture,contributingabout30%ofglobalgreenhousegasemissionsannually.Keyfactorsincludeburningfossilfuelsformachinery,nitrousoxide

2 fromfertilizers,andmethanefromlivestockanddecomposition.Forexample,paddyricefieldscontribute5-20%ofglobalmethaneemissionsduetorapiddecomposition. Industries:Industriesburnfossilfuelsforenergyinmanufacturing,transport,power,andmining,causing43%ofglobalgreenhousegasemissions.Factoriesmakinggoodslikecementandsteelreleasecarbondioxidefromburningcoalandgas.Transportinggoodswithtrucks,ships,andplanesalsoaddsemissions,whilepowerplantsandminingactivitiescontributefurthercontributetoglobalwarming. Urbanisation:Incities,fossilfuelspowervehiclesandhouseholdactivitieslikeheating,cooling,andlighting.Forexample,citiesconsume78%ofglobalenergyandsignificantlycontributetogreenhousegasemissions. ======================================================================= Impactsofclimatechange(naturalandhumansystems) Naturalsystems(Increaseinatmosphericandoceansurfacetemperatures,changesinoceancirculation,changesinprecipitationonland) Aquaticecosystems(Threatstocoralreefs,oceanacidification,disruptionofmarinefoodwebs) Terrestrialecosystems(Threatstofloraandfauna,changesinextremeweatherincludingdroughtsandexcessiverainfall) ————————————————————————————————————————— Naturalsystems (A)-Increaseinatmosphericandoceansurfacetemperatures:Mostoftheheattrappedbygreenhousegasesisabsorbedbyoceans.Thisresultsinincreaseofaverageoceantemperatures.TheEarth'saveragesurfacetemperaturehasincreasedbyapproximately1.1°Csincethelate19thcentury.Highertemperaturesreducecropyieldsbyshorteninggrowingseasons,thiscancausefoodshortages.Seasurfacetemperatureshaveincreasedbyabout0.13°Cperdecadesince1901.Oceanshaveabsorbedover90%ofexcessheatfromglobalwarming.Warmerwatersdisruptfishbreeding,migration,andfeeding,leadingtosmallercatches.(LEADStopointD) (B)-Changestooceancirculations:Climatechangeisexpectedtoslowdowntheglobaloceancirculation,wateratthesurfacegainsheatduetorisingatmospherictemperaturesandbecomeslessdense.Thesinkingofwateratthepolesisthusreducedwhichslowsdowntheflowofwater.Forexample,theoceancurrentintheAtlanticOceanhasslowedbyabout15%,theAtlanticcodrelyoncold,nutrient-richwatersforspawningandfeeding.Aslowdowncouldwarmtheirhabitats,reducingpopulationsizeanddistribution.Increasingfoodshortagesinsomepartsoftheworld. (C)-Changesinprecipitationonland:Climatechangealtersprecipitationpatterns,causingwetregionstobecomewetteranddryregionstobecomedrier.Increasedevaporationinwarmer,wetterareasincreasesatmosphericwatervapour,leadingtoheavierrainfall.Forexample,Bangladeshisalow-lyingcountrypronetoheavymonsoonrainsandflooding.ClimatechangecausesBangladeshtoexperiencemorefloods.Incontrast,warmertemperaturesindryregionsenhanceevaporation,reducingsurfacewaterandsoilmoisture,resultinginincreaseddroughtfrequencyandworseningdryconditions.Forexample,Egyptismainlyadesertcountrywithlittlerainfall,relyingontheNileRiverforwaterand

3 agriculture.ClimatechangewillresultinEgyptexperiencingmoredroughts.(LEADSTODIRECTIMPACTSTOHUMANSYSTEMSPOINTBANDC)————————————————————————————————————————— Aquaticecosystems (D)-Threatstocoralreefs:Increasedoceantemperaturesfromclimatechangecancausealgaetoleavecorals,leadingtobleachingandahigherriskofcoraldeath.Coralreefsprovidehabitatsandfoodformillionsofmarinespecies,likefishandseaturtles.Whencoralsdie,thesespecieslosetheirsourcesoffoodandshelter,disruptingtheentireecosystem.Forexample,theGreatBarrierReefinAustraliawasseverelyaffectedinto2016and2017duetorisingseatemperatures,uptotwo-thirdsofcoralsdieinthenorthernsectionofthereef,speciesdiversitysubsequentlydecreased.(EffectsofpointA) (E)-Oceanacidification:Oceansareimportantnaturalcarbonsinksduetothepresenceofphytoplanktonswhichabsorbcarbondioxidewhentheyphotosynthesise.Theincreaseofcarbondioxideemissionsleadstoincreaseinoceanacidity.Carbonicacidsdissolvecalciumcarbonatewhichisneededbyaquaticorganismssuchascoralstoformtheirskeletons.Atthisrate,coralreefsareerodingfasterthannewcoralscanform.Thiscancausespeciesthatdependonthemforfood,habitatandshelterfrompredatorstobenegativelyaffectedandmaypotentiallygoextinct.Forexample,averagecoralcoverintheGreatBarrierReefhasdroppedtoabout30%ofwhatiswasinthe1960s,inpartduetooceanacidification.Astherateofoceanacidificationincreases,moremarinespeciesmightdieoffduetolackoffoodornoplacetohidefrompredatorswhichresultsindeath.(LeadstopointD,impactsofpointA) (F)-Disruptionsofmarinefoodwebs:Increaseinoceansurfacetemperature,alteringthegeographicdistributionofaquaticspecies.Warmingoceansforcespeciestomigratetocoolerareas,suchaspolewardorintodeeperwaters.Equatorialregionswillseeadeclineinbiodiversity,whilepolarregionswillexperienceanincrease.Forexample,tropicalspeciessuchasparrotfishandrabbitfishhavemigratedpolewards.Astudyfoundthatdiversityforspeciesintropicalwatershasdroppedsignificantlyinthelast50years.Thus,therewillbeachangeincompositionofaquaticecosystemwhichmightresultinfoodshortagesinsomepartsoftheworld. —————-———————————————————————————————————— Terrestrialecosystems (G)-Threatstofloraandfauna:Climatechangeincreasesatmospherictemperatures,causingterrestrialspeciestomigratetowardhigherlatitudesandaltitudeswhereit'scooler.Forexample,about170speciesofbirdstrackedinNorthAmericahaveexpandedtheirrangenorthwardsby50kmonaverageduringthepast4decadesandtemperateforestsareadvancingnorthwardsandreplacingborealforests,whileborealforestsareadvancingnorthwardsintothetundra.Thisdisruptsterrestrialecosystemsasmountainspeciesthatprefercoldenvironmentsmayhavenoplacetogoifthemountaintopistoowarmforthem.Theywillcompetewithspeciesmovingupward,increasingextinctionrisks.Plantsunabletoadaptormigratewillalsodecline. (F)-Impactsofdroughtsonfloraandfauna:Plantsarevulnerabletodroughtsastheycannotmoveforwater,leadingtowiltinganddeath.Weakenedplantsaremoresusceptibletodiseasesandpests.Forinstance,