28-ClimateChange-Control-II -...
Transcript of 28-ClimateChange-Control-II -...
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#28ClimateChangeII-Causes+ExamplesinEarthHistory
Artist’s depiction of Earth during Hadean Eon (~4 billion years ago)
EffectofGreenhouseGasesonClimate-GeologicExamplesGeologicexamplesgenerallyinvolveseveralfactors,notesemphasizemostimportantcontrolsonly.
1)EarlyEarth(4.6-3billionyearsago/b.y.a.orso,earlyPrecambrian)washothouseclimate
EffectofGreenhouseGasesonClimate-GeologicExamples1)EarlyEarth(4.6-3b.y.a.orso,hothouse)EarlyEarth’satmospherehadfollowingcharacterisGcs:
EarlyEarth CurrentEarth
AtmosphericCO2abundance 98% 0.04%
AtmosphericPressure 60 1
Temperatureaverage 290°C 16°C
WhywasearlyEarthsohot? ~200,000GmesmoreCO2
WhysomuchCO2inatmosphere? VolcanicerupGonsMUCHmorecommon
WhathappenedtomostoftheCO2inearlyEarth’satmosphere?
MostofcurrentEarth’scarboninlimestone(needliquidwatertoform)
EffectofGreenhouseGasesonClimate-GeologicExamples1)EarlyEarth(4.6-3b.y.a.orso,hothouse)HighCO2levelsinearlyEarth’satmosphereduetoMUCHmorefrequentvolcanicerupGons
Artist’s depiction of Earth during Hadean Eon (~4 billion years ago)
EffectofGreenhouseGasesonClimate-GeologicExamples1)EarlyEarth(4.6-3b.y.a.orso,hothouse)
TodaymostcarbononEarthisinrock(limestone)
EffectofGreenhouseGasesonClimate-GeologicExamples2)EndofMesozoic/beginningofCenozoic(100-50m.y.a.)washothouseclimate,resultedinfloodingofmuchlandonconGnents(glaciersmelt,sealevelrises)
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EffectofGreenhouseGasesonClimate-GeologicExamples2)EndofMesozoic/beginningofCenozoic(100-50m.y.a.)hothouseMajorreasonforwarmclimateishighlevelsofatmosphericCO2(7-10xtoday'slevel)from↑volcanismbyrapidseafloorspreadingassociatedwithopeningofAtlanGcOcean
EffectofGreenhouseGasesonClimate-GeologicExamples3)CenozoicCooling(50-2m.y.a.)-aberhothouseclimate,Earthcooledprogressively
Majorfactorduetoplatetectonics;Beginning~45m.y.a.,IndiabegantocollidewithEurasia,resulGnginenormousmountainrange(Himalayas)
EffectofGreenhouseGasesonClimate-GeologicExamples3)CenozoicCooling(50-2m.y.a.)-CreaGonofenormousmountainrangeexposedenormousamountofsilicateandcarbonaterocktochemicalweathering.Steepslopeserodequickly,exposingnewfreshrock.Chemicalweathering<levelsofCO2gas,causingglobalcooling