global warmming in usa

8/9/2019 global warmming in usa

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Global Warming

(Climate Change)


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Outline of Lectures

• Earth’s Energy Balance

– incident solar energy – outgoing longa!e radiation

– detailed energy balance

• Greenhouse Gases – the greenhouse effect" and G#Gs

– increasing G#Gs – biogeochemical cycles$ the carbon cycle

• %adiati!e &orcing' the Enhanced Greenhouse Effect – elanation of the concet of radiati!e forcing

– current !alues of radiati!e forcings

• Climate Change' *rends and +redictions – ast global a!erage temerature trends – feedbac, effects- &actors dri!ing climate change-

– comuter models

– redictions' global arming and other changes in climate


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Earth’s Energy Balance

.ncoming /olar Energy

stri,es the earth

(aroimate)cross0sectional area

1-2 13 W12

emits

in all directions4-5 13 W

67

• to maintain energy balance" Earth must also emit energy at the

same rate of 1-2 1312 89s

• di!iding by the surface area" this a!erages out to 4:6 W9m6


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.ncoming and Outgoing %adiation


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• Lecture Question

– #o much of the sunlight that reaches the earth is'

a) reflected ithout being absorbed;

b) absorbed by the atmoshere;

c) absorbed by Earth’s surface;

a) 43<

b) 6=<

c) :=


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•about 43< of

incoming sunlight isreflected bac, to

sace (clouds"

oceans" sno9ice)

•this is Earth’s albedo

•the amount a!ailable

to heat the earth is235 W/m2

•about 6=< is

absorbed by the

atmoshere (see

figure on left)

•the rest (about :=


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*he Greenhouse Effect

• Lecture Questions

– What is the greenhouse effect ; – What are greenhouse gases (G#Gs);

– What are the fi!e main natural G#Gs;

– (ansers to follo)

– Without the greenhouse effect" the global a!erage surface temerature of theEarth ould be about 01> ?C instead of 1= ?C-


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Outgoing Longa!e %adiation (OL%)

*he ma@or natural

G#Gs are

•ater (#6O)

•carbon dioide (CO6)

•oAone (O4)

•methane (C#:)

•nitrous oide (6O)

(not shon on left)

•note the IR Window

in the OL% (5014 µm)

•G#Gs absorbing in

this region tend to be

!ery effecti!e at

traing OL%


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Earth’s Energy Balance: etailed Balance

Earth's Surface=66 inut D =66 outut

Atmosphere (air + clouds)=1> inut D =1> outut

34210

30

!

1!" 102 350 324 40

1#5

235

$op of the Atmosphere

reflected solar

radiation

incident solar

radiation

outgoing longwave

radiation (OLR)

non-radiative

heat transfer


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*he Enhanced Greenhouse Effect


– What is the enhanced greenhouse effect;

– *he enhanced greenhouse effect is an increase in the amount of

energy traed by the atmoshere" largely due to increased

concentrations of greenhouse gases-

– What G#Gs ha!e been increased in the atmoshere due to

human acti!ities;

– CO6" C#:" 6O" troosheric O4 (smog)" and halocarbons(C&Cs" #C&Cs" #&Cs" halons" and other cds)


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1>73 1>23 1>53 1>>3 6333

C O 6

C o n c e n t r a t i o n " ) ) m

413

463

443

4:3

4=3

473

423

453

Fonthly Feasurements at Fauna LoaFonthly Feasurements at the /outh +ole

The lobal !arbon !ycle

.ncrease in tmosheric CO6

What do you see in these data?


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.ncreasing G#G Concentrations


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*he Global Carbon Cycle


– What is the carbon cycle; – What are the main rocesses that contribute to the carbon cycle;

– lobal Biogeoche"ical !ycles

• Fost imortant cycles' carbon (usually ta,en to be carbon dioide)" nitrogen"

sulfur" hoshorus" ater

• Earth is di!ided u into a number of distinct reser!oirs (HboesI) such as'atmoshere" ater" land" etc-

– i!isions can be finer than this- &or eamle" the atmoshere can be further

subdi!ided into trooshere and stratoshere$ the hydroshere can be di!ided

into oceans and freshater (and these can be further subdi!ided)" etc-

– *he amount of the element in each reser!oir is esimtated in some manner-

• *he rocesses that allo echange of the element between the reser!oirs

are described and their rates are Juantified – &or the carbon cycle" the most imortant rocesses are' hotosynthesis"

resiration9decay" combustion" dissolution9outgassing" CaCO4 (calcite) formation

and dissolution


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Biogeochemical Cycles

A$%&SEE

*&SEE

(!egetation" animals"microorganisms)

,-&SEE

(oceans" la,es"

ri!ers" groundater)

.$&SEE

(soil" sediment" crust)

decay

assimilation

runoff

assimilation

decay"

burial

outgassing

dissolution

&/$E SAE

-EE EA$

(mantle" core)

subduction !olcanoes

resiration hotosynthesis

escae meteorites

sur#ace reservoirs


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Fain Comonents of the Natural Carbon Cycle

Source: IPCC

Knits' 131= g C or 131= g C9yr


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#uman cti!ities and

G#G .ncreases in the tmoshere• Lecture Question

– *he atmosheric concentration of the folloing G#Gs ha!e beenincreasing due to human acti!ities- &or each one" state the ma@oracti!ities that ha!e caused the increase'

• CO6

• C#:

• 6O

• troosheric O4• halocarbons

• CO6' fossil fuel combustion" deforestation (biomass burning)" cementroduction

• C#:' coal mining" rice addies" li!estoc," landfills" biomass burning" seagetreatment

• 6O' fertiliAer use" roducing nutrient ollution that stimulates nitrificationand denitrification" both of hich gi!e 6O as a byroduct

• trooshere O4' main comonent of hotochemical smog" roduced by Oemissions (cars" oer lants) and reacti!e !olatile organic cds (OCs)

• halocarbons' used as refrigerants" fire etinguishers" sol!ents" etc


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#uman +erturbation of the Global Carbon Cycle


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Fodeling the Carbon Cycle (Fass Balance)

Anthropogenic sources

fossil fuel combustion"cement roduction

=-= M 3-= +gC9yr

changes in land0use 1-7 M 1-3 +gC9yr

total e"issions $%& ' &%& (g!)yr

Partitioning aong reservoirs

net ocean uta,e 6-3 M 3-5 +gC9yr

net land uta,e 1-5 M 1-7 +gC9yr

net storage in at"os*here (easured )

+%+ ' ,%& (g!)yr


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%adiati!e &orcing

• Lecture Nuestion

– What is radiative forcing ;

– )adiati1e forci is a !uantitative easure of the imbalance

beteen incoming (solar) and outgoing (reflected lus infrared)

radiation-

– positive radiati!e forcing indicates an increase in the amount

of radiation traed by the atmoshere (an enhanced

greenhouse effect)" e!entually leading to global arming-

negative forcing e!entually leads to global cooling-


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%adiati!e &orcing


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%adiati!e &orcing

• Lecture Nuestions

– What ha!e been the ma@or (direct) factors that ha!e caused aositi!e forcing in the ast century;

• increases in concentrations of CO6" C#:" halocarbons" troosheric

O4" and 6O

• increase in elemental carbon +F (ie" soot)

• increase in solar outut

– What factors ha!e caused a negati!e forcing;

• stratosheric oAone deletion" increases in most +F (es sulfate)"

changes in cloud formation rocess" increased albedo due to land0

use changes


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%adiati!e &orcing


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%adiati!e &orcing


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Global Warming

• Lecture Nuestion

– What has been the a!erage global surface temerature increasein the last century; What is the current rate of increase er

decade;

– .+CC and tetboo,' the global a!erage surface temeratures

o!er land increased by about 3-7 ?C (beteen 3-: ?C and 3-5 ?C)

– .+CC' the current rate of increase is about 3-14 ?C 9 decade in

daytime daily ma temeratures-


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*emerature ata – irect Feasurements


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*emerature ata – .ndirect Feasures


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*emerature ata – Long *erm ariability


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*emerature – CO6 Correlation

Historical Record from Vostok Ice Core

Temperature and Carbon Dioxide Data

ge" ,yr B+

3 133 633 433 :33

* e m ) e r a

t u r e e ! i a t i o n f r o m +

r e s e n t " o C

016

013

05

07

0:

06

3

6

:

C O 6

c o n c e n t r a t i o n " ) ) m

173

153

633

663

6:3

673

653

433

463

temerature

carbon dioide


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Climate Change Contro!ersies• *he Greenhouse effect

– Fechanism is not contro!ersial

• .ncreasing G#G concs – *he increase itself is not contro!ersial – or is it contro!ersial that it is due to human acti!ities

• %adiati!e &orcing – *he fact that increasing G#Gs ill result in a ositi!e forcing is not contro!ersial – *here is some (fairly small) uncertainty in the magnitude of the forcing due to

G#G increases

– *here is larger uncertainty on the effect of other changes (esecially aerosolindirect effects) on forcing

• *emerature *rends – Generally acceted that global a!erage surface tems are rising – /ome contro!ersy regarding samling bias" satellite readings$ largely resol!ed

no- – &airly broad agreement that the obser!ed arming trend is not due to natural

factors only (although they contribute)

• &uture +redictions – &irtually certain that increasing G#G concs ill eventually lead to arming – %ate and magnitude of the increase are uncertain$ greatest source of uncertainty

is emission rate of CO6 and other G#Gs

– *he e##ects of increasing temerature are also contro!ersial (ie" ho bad ould

arming really be;)


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.+CC /tatements

• What is the .+CC

– .ntergo!ernmental +anel of Climate Change – KE+0WFO

– uthoritati!e scientific body to assess current status of climate changescience

– lso loo,s at mitigation (technology" olicy" economics)

• /econd ssessment %eort (/%)" 1>>7 – #$he "alance of evidence suggests a discerni"le huan influence on

glo"al cliate%&

• *hird ssessment %eort (*%)" 6331 – #$here is ne' and stronger evidence that ost of the 'aring o"served

over the last () years is attri"uta"le to huan activities%&

• &ourth ssessment %eort (%:)" 6332 – HWaring of the cliate syste is une!uivocal*+there is, very high

con#idence that the glo"ally averaged net effect of huan activitiessince -.() has "een one of 'aring -I

• ote' H!ery high confidenceI is secified as Hat least >3< robable-I


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/tatements by K/ OrganiAations

• merican Feteorology /ociety (F/)" 6334

– Because greenhouse gases continue to increase" e are" in effect"conducting a global climate eeriment" neither lanned nor controlled"

the results of hich may resent unrecedented challenges to our

isdom and foresight as ell as ha!e significant imacts on our natural

and societal systems-

• merican Geohysical Knion" 6334

– #uman acti!ities are increasingly altering the Earths climate- *hese

effects add to natural influences that ha!e been resent o!er Earths

history- /cientific e!idence strongly indicates that natural influences

cannot elain the raid increase in global near0surface temeratures

obser!ed during the second half of the 63th century-

• Other K/ organiAations ho ha!e issued similar statements – ational cademy of /cience

– merican ssociation for the d!ancement of /cience


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/ome +oints Fade by /,etics

• *he science is too uncertain

– .+CC statements do not reflect the true degree of uncertainty• /cience is not a democracy

– lthough a ma@ority of scientists belie!e global arming is realand is due largely to human acti!ities" that does not mean theyare correct

– Finority scientific oinion has been right before – *he science has been oliticiAed

• +ast temeratures – *he Earth has been both cooler and armer than today

• +redictions are too uncertain

– We cannot base olicy on them• Pyoto is a flaed treaty

– Fore cost0effecti!e to ait before regulating G#G generation

• Warming is not so bad


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+redictions for the &uture


– What does the .+CC redict ill haen to the global a!eragetemerature in the net 133 years;


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• Questions

– #o are future temeratures redicted;• /ohisticated /eneral Circulation 0odels (GCFs) are used-

– Commonly called HGlobal Climate FodelsI

– Comuter0based integration of the echange of energy and matter in a

40dimensional satial grid- *hey are run forard in time" and future

trends in climate (temerature" reciitation" etc) are redicted for each

element of the grid-

– ery many rocesses must be considered (see net slide)

– onlinear feed"ac1 effects must also be considered-

– #o are redictions !erified;

• Fodel redictions can be made for ast climates and comared to

the actual measurements that ere collected-


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&actors ri!ing Climate

bold arrows re*resentas*ects that "ay change


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&eedbac, Effects

• What are feedbac, effects;

– negative feedbac, is one that tends to damen changes – positive feedbac, is one that tends to reinforce changes

• Eamles (not inclusi!e)' effects of increasing temerature on – *he carbon cycle

• decreases solubility of CO6 in ater" decreasing the ocean uta,e rate

• ossibly increases the rate of hotosynthesis and lant groth

• increases the rate of decomosition

– *he hydrologic cycle• increases ater !aor ressure" increasing conc of ater in the atmoshere

– Earth’s albedo• increases cloud co!er

• decreases sno co!er – Energy circulation

• atmosheric circulation

• oceanic (thermohaline) circulation

GC


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+redictions' GCFs

• What are GCFs;

– Global Climate Fodels or eneral !irculation 1odels – GCF Haims to describe geohysical flo by integrating a

!ariety of fluid0dynamical" chemical" or e!en biological eJuationsthat are either deri!ed directly from hysical las (e-g- etonsla) or constructed by more emirical means-I (Wi,iedia)

– *here are GCFs for ocean and atmosheric comonents$couled atmosheric0oceanic GCFs (OGCFs) can be used toma,e climate redictions

– Fost sohisticated GCFs are 40dimensional HgridsI to modelfluid motion

– .deally ro!ide both regional and global redictions of climate

– *he models are imerfect

• *rue of any model" but'

• Critics of global arming theory content that the imerfections aresignificant


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+redictions erification' atural &orcings Only

f O


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+redictions erification' #uman &orcings Only


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Oth Eff t Gl b l Cli t


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Other Effects on Global Climate


– Other than arming" hat other changes are redicted in globalclimate in the net century; – /ea le!el ill rise

• 3-15m – 3-=>m (%:) by 6133 by thermal eansion" hich ill continuefor centuries

• +otentially much larger increases due to loss9shifts of landloc,ed icesheets such as in Greenland (comlete elimination ould lead to 2m

rise) and ntarctica – +reciitation ill increase in some areas" decrease in others

• +ossible increase in high latitudes and decrease in subtroical regions

– .ncrease in freJuency and intensity of HetremeI climate e!ents• #eat a!es" hea!y reciitation e!ents" tornados" hurricanes" stronger

El ino e!ents" monsoons" etc

– Effects on ecosystems uncertain• ranges of !arious organisms ill change• increased sread of infectious disease (es insect0borne) ossible• decrease in biodi!ersity feared

– Circulation in the tlantic Ocean (FOC) ill slo

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global warmming in usa