7/29/09

1

Heatin,HeatOut Toocold

•  IfalltheheatcominginwentouttheaveragetemperatureontheEarth’ssurfacewouldbe

‐19

How?

•  Somemoleculesabsorbtheheatcomingupfromtheearth,

•  TheythenreemitininrandomdirecFons–50%ofitcomesback.

Someofthegasesthatdothisareincreasing–alot! Anditis:

7/29/09

2

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

3

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