Lecture for Wednesday Aug 27

Lecture:GlobalwarmingtheoryCauses/Consequencesofclimatechange

Ac*vity:Mediaandclimatechange

ReadingforTomorrow:Houghtonp56‐68

Visible and Infrared Satellite Pictures

a)Whichisthe"visible"image?Howcanyoutell?

d)Ontheinfraredimage,arehighertemperatureslighterordarker?Howcanyoutell?

c)WhichismorereflecJve:oceanorland?

infrared(LW) visible(SW)

b)WhatisemiKngtheradiaJonineachcase?

Height

Temperature

Lowest10koftheatmos.(wheremostofthemassis)temperaturedecreaseswithheight

Wherearetheclouds?

Whyisthesurfacewarm?

Whyisthestratospherewarm?

Medium

cold

Earth

Fromsatellite:warmareasareprobablyatorclosetothegroundandcoldareasareprobablytallcloudtops

warm

IRSatelliteViewExplained

Emission/AbsorpJon

Earthandcloudsare“blackbodies”‐emitandabsorbwithperfectefficiency(solidcurve)

GHG‐HypotheJcalimperfectEmiXer/absorberatThesameT

PeakwavelengthindicatestemperatureIsabout15degC

FluxorRa

diance(W

/m2 )

200

0

Wavelength(micrometers)

15 20

100

25

ButEarthisgenerallywarmerthanatmosphere

GHG‐peakindicatesT=‐15C

EarthpeakwavelengthIndicatesT=15degC

FluxorRa

diance(W

/m2 )

200

0

Wavelength(micrometers)

15 20

100

25

LWSpectrumofEarthwithAtmos.

SeedipsatwavelengthswhereGHGaregoodabsorbers/emiXers.ThecurvedipsbecausetheGHGarecolderthanthesurface

HoughtonFig2.4

WhereGHGarebadabsorbers/emiXers,thefluxfromthesurfacepassesthroughtheatmosphere“window”

AddingmoreGHG,shrinksthewindowsAndlowerstheoutgoingLWflux

PlanetaryEnergyBalance

AtEquilibrium(asteadyclimate):

EnergyFluxin=EnergyFluxout FIN=FOUT

Foraplanet:

Absorbedsolarenergy=Heatenergylosttospace*

*dependsontemperatureT

oftheearthandatmosphere

Houghton Fig 2.6

343‐103=240(W/m2) 40+35+165=240 (W/m2)

visiblesatelliteimage

infraredsatelliteimage

FIN=FOUT?

MainCons*tuentsofEarth’sAtmosphere

N2Nitrogen 78%

O2Oxygen 21%

ArArgon 1%

H2OWaterVapor 0‐4%

CO2CarbonDioxide 0.0385%(increasing)

Whichonescontributetothegreenhouseeffect?

LikeHoughtontable2.1

Houghton Fig 2.2

• Termcomesfrom1827Jean‐BapJsteFourier

• Absorbedsunlightheatsplantsandsoil

• PlantsandsoilemitIRandheatglasswall

• GlasswallsemitIRbacktowardsplantswarm

TheGreenhouseEffectGHE

glass

Houghton Fig 2.2

Notreally,becausethemainreasonagreenhouseiswarmisbecausetheytraprisingwarmair

Absorbedsunlightcauses“thermals”

ResultsinconvecJon=risingwarmairandsinkingcoldair

warm

IstheGHELikeAGreenhouse?

glass

ASlightlyBecerFigureFortheGHE

Houghton Fig 2.5

greenhousegases

Earth'ssurface

Warm

Cold

Warm

ConsiderEarthwithNoAtmos.

Earth

SW LW

HereIhaveletarrowlengthsindicaterelaJveamountofflux.Earthisinbalance.

ReasonableesJmatesgivesanaveragetemperaturebelowfreezing!

EarthwithaSimple1‐LayerAtmos.

Earth

SW LW

SimpleAtmosphere

GHE

The Greenhouse Effect: Tyndall JohnTyndall*,1862(riveranalogy):

"Asadambuiltacrossarivercausesalocaldeepeningofthestream,soouratmosphere,thrownasabarrieracrosstheterrestrialrays,producesalocalheighteningofthetemperatureattheEarth'ssurface."

*Bri*shphysicist,chemist,inventor,andearlyatmosphericscien*st;measuredabsorp*onspectraofvariousgasesandscaceringproper*esofgasesandpar*cles;discoveredchemicalnatureofozone;firsturbanairqualitystudies

TheGreenhouseEffect

Makesuswarmerby20to30C

Itisonlynatural!ItisnolongerdebatedbyscienJsts

Blanketsalsowarmbyreducingconvec*on.

Houghtonusestheterm“radia*onblanket”

Human‐inducedglobalwarming:addmoreblankets?

IstheGHELikeABlanket?

Current paradigm –forcing

10,000 5,000 0Yearsbeforepresent

CharlesD.Keeling(1925‐2005)

CO2hasrisenbyover35%

IPCC WG1 SPM Fig 1

EnhancedorAnthropogenicGHE

Earth

SW LW

SimpleAtmosphereX TooSimplebecauseitdoesn’tchangeiftherearemoreGHGs

Rememberthattheatmosphereiscolderalop

IncreasingtheGHGconcentra*onreducestheoutgoingLW(coldmaceremitslessheatthanwarmmacer.

AddingmoreGHGislikeaddingmorehighclouds.

Lessheatescapes,so

FOUTdecreases

Atfirst,energyisnotinbalance

WhichisbiggerFINorFOUT?

ImaginetheCO2LevelDoubledInstantly

Lessheatescapes,so

FOUTdecreases

“Radia*veForcing”

ΔF=FIN‐FOUT=3.7W/m2

(es*matedtowithinafewtenths)

Energybalancetheoryofclimatechange

ΔT = λ ΔF

Note: Δ: common symbol to refer to change in some quantity

ΔF: radiative forcing (change in energy balance) ΔT: response (change in surface temperature) λ: climate sensitivity (everything else)

TheOnlyEqua*onYouNeedtoKnow

λ: does not represent the wavelength of light here!

Energybalancetheoryofclimatechange

ΔT = λ ΔF

RunaClimateModelwithDoubleCO2

RunmodelunJltheoceancomesintoequilibriumwiththeatmosphereandfindΔT isabout2‐4.5degC.

Soλ is?

WhyCan’tWeUsetheRealEarth?

Currentparadigm–forcing

Source: IPCC 2001 WG1, SPM, Fig 4

Response:ObservedWarming

WeCANNOTUsetheRealEarthVeryEasily

BecausetheforcingisnotjustfromCO2

AND

Theoceanisnotinequilibriumwiththeatmosphere,sothefullsurfacewarmingisdelayed

New York Times Climate Experts Tussle Over Details. Public Gets Whiplash.

By ANDREW C. REVKIN July 29, 2008

Revkin writes, “How fast is Greenland shedding ice? Did human-caused warming wipe out frogs …? These questions endure even as the basic theory of a rising human influence on climate has steadily solidified.”

“Scientists see persistent disputes as the normal stuttering journey toward improved understanding of how the world works.”

Remind you of something Prof Ackerman said?

Example: Are Hurricane strengthening from global warming? Many papers on both sides of debate.

“ “not as an evolution of objective scientific understanding but as a proliferation of contradictory opinions.” ” according to W. Tad Pfeffer.

Are scientists partly to blame for public disengagement? A public divided and confused?

Revkin writes, “Morris Ward, the editor of the Yale effort says that it will be up to the public to choose to be better informed on momentous issues that do not fit the normal template for news or clash with their ingrained worldviews. “At some point,” he said, “the public at large has to step up to the plate in terms of scientific and policy literacy, in terms of commitment to education and strong and effective political leadership, and in terms of their own general self-improvement.” ”

Revkin writes, “The news media sometimes overplayed the uncertainty by balancing opposing views in a story without characterizing the overall level of confidence in either side”

The Columbia Journalism Review's Division Over Dissent IS GLOBAL WARMING NOW BEYOND DEBATE?

By Ron Rosenbaum Posted Friday, Aug. 8, 2008, at 6:09 PM ET

Rosenbaum criticizing other article that says, “Scientists look for consistency among several reports before concluding something is true.”

June 27, 2008 North Pole could be ice-free this summer, scientists say

By Alan Duke CNN

"We kind of have an informal betting pool going around in our center and that betting pool is 'does the North Pole melt out this summer?' and it may well," said the center's senior research scientist, Mark Serreze.

A more conservative ice scientist, Cecilia Bitz at the University of Washington, put the odds of a North Pole without ice closer to 1 in 4. Even that is far worse than climate models had predicted, which was 1 in 70 sometime in the next decade, she said.

But both she and Serreze agree it’s just a matter of time.

The first scene from 31 January 2002 shows the shelf in late austral summer with dark bluish melt ponds dotting its surface. In the next two scenes minor retreat takes place, amounting to about 800 km2. The main collapse is seen in the last two scenes, on 5 March and 7 March. The last phases of the retreat totaled ~2600 km2.

In-class activity: Enhanced GHE EnergybalanceequaJon…

FOUTenergy emitted

by Earth

FINenergy absorbed

by Earth

=

IfyouaddCO2totheatmosphere,whichtermchangesanddoesitincreaseordecrease?

“GlobalWarmingTheory”

Step 1: GHG increases, FOUTinstantly decreases, so FOUT < FIN

Step 2: In time Tsurface will go up until balance is restored, because

surface warming makes FOUT go up again

What is the change to the top of atmosphere radiation balance in

step 1 known as:

ΔF = FOUT-FIN ?

Radiative Forcing Or Climate Forcing

Source: IPCC 2007 WG1, SPM, Fig 2