The importance of longevity in a greenhouse gas as climate forcing
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The importance of longevity in a greenhouse gas as climate forcing. David Archer University of Chicago. Joseph Fourier. Joseph Fourier described the greenhouse effect in 1827. Memoires d l’Academie Royale des Sciences de l’Institute de France VIIII, 570-604 (1827).

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The importance of longevity in a greenhouse gas as climate forcing

The importance of longevity in a greenhouse gas as climate forcing

David Archer

University of Chicago


Joseph fourier

Joseph Fourier

Joseph Fourier described the greenhouse effect in 1827

Memoires d l’Academie Royale des Sciences de l’Institute de France VIIII, 570-604 (1827)


Energy balance of a bare rock

Energy Balance of a Bare Rock

Tearth = 259 K = -14° C = 6°F


A planet with an atmosphere

A Planet with an Atmosphere

Tatm = 259 K

Tearth = 303 K = 86° F


John tyndall 1859

John Tyndall, 1859

John Tyndall discovered that CO2, H2O, and CH4 are

greenhouse gases. O2 and N2 are not.


Co 2 is a greenhouse gas

CO2 is a greenhouse gas

Resting State

Symmetric Stretch

O

C

O

C

O

O

No Resting Dipole

IR

Inactive

Asymmetric Stretch

Bend

C

O

O

O

C

O

-1

-1

2349

cm

660

cm


Earth s outgoing infrared spectrum

Earth’s outgoing infrared spectrum


The band saturation effect

The band saturation effect


Radiative forcing goes as ln co2

Radiative Forcing goes as ln(CO2)


Svante arrhenius

Svante Arrhenius

Svante Arrhenius calculated that doubling CO2would warm the Earth by 4-6°C, in 1896


The water vapor feedback

The water vapor feedback

+

W

a

t

e

r

V

a

p

o

r

F

e

e

d

b

a

c

k

W

a

t

e

r

V

a

p

o

r

C

o

n

c

e

n

t

r

a

t

i

o

n

+

T

e

m

p

e

r

a

t

u

r

e


The runaway greenhouse effect

The Runaway Greenhouse Effect


The ice albedo feedback

The ice albedo feedback

+

I

c

e

A

l

b

e

d

o

F

e

e

d

b

a

c

I

c

e

M

e

l

t

s

+

T

e

m

p

e

r

a

t

u

r

e


David keeling

David Keeling

David Keeling started measuring CO2

concentration in the atmosphere


The biosphere breathes

The biosphere breathes


The importance of longevity in a greenhouse gas as climate forcing

Various public predictions of detectable human-caused warming by year 2000

Charney report and others


Climate forcings

Climate forcings

Only greenhouse gasforcing looks like therecent temperature rise.

Crowley, 2000


What about phenomena undreamed of

What about phenomenaundreamed-of?

The sun is good at pushing our climate buttons.

Clouds? Humidity?

“They blame CO2 because they can’t think of anything else.”


A detective story

A detective story

The Butler. Found holding a smoking gun next to the deceased. Forensics matches the gun with the bullets.

The Chauffer. In Kentucky for sister’s wedding. “Can’t think of any way he could have done it.”

To convict the Chauffer, we’d have to first unconvict the Butler.


Airborne fraction of fossil fuel co 2

Airborne fraction of fossil fuel CO2

Century timescale peak

Airborne Fraction of Carbon Released

Millennial timescale tail


Ipcc 2001 and earlier summaries for policymakers

IPCC 2001 and earlier Summaries for Policymakers

IPCC 2001 and earlier reports implied that global warming would last about a century.


Everyone gets this wrong

Everyone gets this wrong

Rutledge 2011

Shindell, 2012

Ramanathan 2008


Paleocene eocene thermal maximum event 55 myr ago

Paleocene/Eocene Thermal Maximum Event 55 Myr Ago

A natural releaseof CO2, comparableto the potential fossil fuel release.

Warming, with a recovery that took100,000 years.

Zachos et al. 2001


Long tail model intercomparison project ltmip

Long Tail Model Intercomparison Project LTMIP

  • D. Archer, M.l Eby, V. Brovkin, A. Ridgwell, L. Cao, U. Mikolajewicz, K. Caldeira, K. Matsumoto, G. Munhoven, A. Montenegro, Ann. Rev. Earth Sciences, 2009.


Band saturation effect of ir absorbtion by co 2 emphasizes the tail

Band saturation effect of IR absorbtion by CO2 emphasizes the tail

1800

1600

1400

1200

pCO2

1000

800

600

400

200

0

6

5

°C

4

3

2

1

0

0

100

300

400

500

200

kyr


Seawater ph chemistry

Seawater pH Chemistry

CO2 + CO3= + H2O <--> 2 HCO3-

10

100

2000 mM

Concentration in seawater

CO2 uptake capacity is determined by CO3=


Atmosphere ocean equilibrium

Atmosphere / Ocean Equilibrium

600 Gton C

1800 Gton C as CO3=

We expect a partitioningof ~1:3 between air andocean

Gton C = 1015 g


Atmosphere ocean equilibrium1

Atmosphere / Ocean Equilibrium

Airborne Fraction of CO2 Slug

4000-5000Gton

1000-2000Gton

Archer 200522%33%

Lenton 200621-26%34%

CLIMBER22%35%

Goodwin 200724-26%40%Ridgwell 200731%


Atmosphere ocean equilibrium2

Atmosphere / Ocean Equilibrium

Affected by:

changes in circulation

biology

ocean temperature

saturating the carbonate ion buffer


The importance of longevity in a greenhouse gas as climate forcing

Flakiness in ocean / atmosphereequilibrium


Neutralization by caco 3

Neutralization by CaCO3

CO2 + CaCO3 + H2O ==> Ca2+ + 2 HCO3-


How long does it take

How long does it take?

Neutralization e-folding timescale

Archer 20055-8kyr

Lenton 2006500 - 1000 yr

Ridgwell 20071-2 kyr

Tyrell 20072-3 kyr

Pulls the airborne fraction down to ~ 10%


The silicate weathering co 2 thermostat

The Silicate Weathering CO2 Thermostat

Volcanic CO2 degassing

CaSiO2 -> Ca2+ + SiO2

Weathering = function( CO2 )

Ca2+ + CO3= -> CaCO3

CaCO3 + SiO2 -> CaSiO2 + CO2

Burial + Subduction


The importance of longevity in a greenhouse gas as climate forcing

The Silicate Weathering CO2 Thermostat

CO2

>100,000 years

Helps explain Carl Sagan’s “Faint Young Sun” paradox


The importance of longevity in a greenhouse gas as climate forcing

Time scale must be longer than this


Sea level

Sea Level

Sea Level, m

100

Eocene

40

Myr

ago

50

Pliocene

3

Myr

ago

Global Mean T, °C

Today

IPCC

5

10

15

20

Forecast

Year 2100

-50

-100

Last Glacial

Maximum

20

kyr

ago

-150


Methane

Methane


The importance of longevity in a greenhouse gas as climate forcing

Methane is about here

CO2 is here


The importance of longevity in a greenhouse gas as climate forcing

Methane is about here

CO2 is here


Methane1

Methane


Methane2

Methane


Earth s temperature response to radiative forcing

Earth’s temperature response toradiative forcing

RF

Climate sensitivity:

D T / D RF

Upper 100m

Time scale: 10 yrs

Thermal bufferof the deepocean: Time scale 1000 yrs

DeepOcean


Shindell et al 2012

Shindell, et al 2012


Co 2 vs ch 4

CO2 vs. CH4

CO2 poses a “trap” for humanity, because of the time separation of the cause and the impacts, which will continue to worsen essentially forever. It’s like an ever-intensifying curse on our descendents, or planting a cancer.

The climate impacts from CH4 peak and subside within a human timescale.

“Good” cholesterol vs. “Bad” cholesterol?


1 trillion tons of c 2 c peak warming

1 Trillion tons of C => 2 °C peak warming

Allen et al 2009


1 trillion tons of c

1 Trillion tons of C

Already released: 1/2 trillion tons

0.3 from fuels 0.2 from deforestation

Costs (cuts / year) go up if we wait


Fossil fuels are mostly coal

Fossil fuels are mostly coal


Conclusions

Conclusions

No one has a model or theory of climate that explains the present but predicts that global warming won’t happen and be significant.

The impacts of global warming from CO2 will last for millennia (not just a few centuries).

The impacts of short-lived greenhouse gases is attenuated by the slow response time of Earth’s temperature.

Lesson from the past: Sea level is 100x more sensitive to Earth’s temperature on thousand-plus year timescales than the forecast for the year 2100.


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