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