7/29/09
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Heatin,HeatOut Toocold
• IfalltheheatcominginwentouttheaveragetemperatureontheEarth’ssurfacewouldbe
‐19
How?
• Somemoleculesabsorbtheheatcomingupfromtheearth,
• TheythenreemitininrandomdirecFons–50%ofitcomesback.
Someofthegasesthatdothisareincreasing–alot! Anditis:
7/29/09
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So?ItmightmakeCanberra’swintermorebearable…
• Butwearealreadyseeingincreasesin:– Floods– Droughts– Cyclones
• Insomeplacesthemonsoonarefailing• Somediseasesaremorewidespread• Saltisintrudingintogroundwater
And
IceismelFng
Understand the Size of the Challenges
Iceberg B15 calving from the Ross Ice Shelf
295 km
37 km
Satellite Image early March 2000
Measure it 11,000 km2
Understand the Scale of the Challenges
The Edge of B15A
Go in for a closer look Iceberg Alley
7/29/09
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Butwhentheywrotethereportyouhavebeenaskedtoread,noone
thoughtthiswouldhappen
Sealevelsdochange
• Duringthelasticeage(20,000yearsago)sealevelswereabout120mlower.
• 14,000yearsagosealevelsrose20minjust400yearsassomemajoricesheetsmelted.
• Currentsealevelshavebeenremarkablystablesinceabout3000yearsago
• abouttheFmehumansstartedbuildingthings,mostlybythesea.
GreenlandandAntarcFca
• GreenlandisnowclearlymelFngmuchfasterthanpreviouslythought.AntarcFcaprobablyistoo.
• Eachcouldraisesealevelsby5m,that’s10mintotal.Anditcouldhappenwithinthiscentury.
Sowhatmightthislooklike:
• hZp://flood.firetree.net
WillSteffen@ANUsaysthingscanchangeinahurry:
…therapiddisintegraFonofthelargeicesheetsonGreenlandandAntarFcaorlargescaleanduncontrollablefeedbacksinthecarboncycle:acFvaFonofthemethaneclathrates[frozenwaterandmethane]buriedundersedimentsintheoceanfloor,therapidlossofmethanefromwarmeranddriertundraecosystems,increasingwildfiresintheborealandtropicalzones,theconversionoftheAmozonrainforesttosavannah,thereleaseofcarbondioxidefromwarmingsoils…
Whatweareriskingata2degreerise:
• Sealevels• 15‐40%plantandanimalspecies• OceanacidificaFon• WidespreaddroughtanddeserFficaFon• Increasingheatwaves• Monsoonfailure• Glacialwatersupply–AsiaandSouthAmerica• Lossofmajoragriculturallands
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