Global Warming in Geologic Time

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Global WarminginGeologic Time
David Archer University of Chicago
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Joseph Fourier
Joseph Fourier described the greenhouse effect in
1827
Memoires d lAcademie Royale des Sciences de
lInstitute de France VIIII, 570-604 (1827)
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Energy Balance of a Bare Rock
Tearth 259 K -14 C 6F
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A Planet with an Atmosphere
Tatm 259 K
Tearth 303 K 86 F
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John Tyndall, 1859
John Tyndall discovered that CO2, H2O, and CH4
are greenhouse gases. O2 and N2 are not.
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CO2 is a greenhouse gas
Symmetric Stretch
Resting State
C
O
C
O
O
O
No Resting Dipole
IR
Inactive
Asymmetric Stretch
Bend
C
O
O
C
O
O
-1
-1
2349
cm
660
cm
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Water vapor is a greenhouse gas
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Earths outgoing infrared spectrum
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The band saturation effect
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Svante Arrhenius
Svante Arrhenius calculated that doubling CO2
would warm the Earth by 4-6C, in 1896
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The water vapor feedback
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The ice albedo feedback
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Intense warming in high latitudes because of
ice-albedo feedback
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David Keeling
David Keeling started measuring CO2
concentration in the atmosphere
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400
Mauna Loa, Hawaii
390
m
380
p
p

370
,
2
O
360
C
p

c
350
i
r
e
h
340
p
s
o
330
m
t
A
320
310
300
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IPCC
IPCC predicted in 1990 that global warming would
rise above the noise by 2000
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IPCC
IPCC in 1995 found a discernable human
influence on global climate
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Climate forcings
Only greenhouse gasforcing looks like therecent
temperature rise.
Crowley, 2000
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What about phenomenaundreamed-of?
The sun is good at pushing our climate buttons.
Clouds? Humidity? They blame CO2 because
they cant think of anything else.
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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
sisters wedding. Cant think of any way he
could have done it. To convict the Chauffer,
wed have to first unconvict the Butler.
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What happens to fossil fuel CO2
Century timescale peak
Airborne Fraction of Carbon Released
Millennial timescale tail
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One gallon of gasoline Usable energy 2500
kcal Unwanted greenhouse energy over CO2
lifetime
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One gallon of gasoline Usable energy 2500
kcal Unwanted greenhouse energy over CO2
lifetime 100,000,000,000 kcal
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Avoiding Dangerous Climate Change
If the peak contains 50 of the emitted CO2, and
climate sensitivity DT2x 3 C, then we could
emit 700 Gton C and avoid warming greater than
2 C. We have already emitted 300 Gton C. Oil
Gas 400 Gton C. Just stop burning coal.
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How Long will Global Warming Last?
IPCC 2001 and earlier reports implied that
global warming would last about a century.
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IPCC 2007 Summary for Policymakers
Carbon dioxide cycles between the atmosphere,
oceans andland biosphere. Its removal from the
atmosphere involves arange of processes with
different time scales. About 50 of a CO2
increase will be removed from the atmosphere
within 30 years, and a further 30 will be
removed within a few centuries. The remaining 20
may stay in the atmosphere for many thousands of
years.
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Airborne Fraction
4000-5000 Gton C Release
Peak
1 kyr
10 kyr
CLIMBER 67 57 26 Archer 2005 60 33 15
Lenton 2006 67-75 14-16 10-15 Ridgwell
subm. 50 34 12 Tyrell 2007 70 42 21
Atmosphere / Ocean / Weathering / CaCO3 models
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Airborne Fraction
1000-2000 Gton C Release
Peak
1 kyr
10 kyr
CLIMBER 45 31 14 Archer 2005 58 24 11
Lenton 2006 50-63 17-19 11
Atmosphere / Ocean / Weathering / CaCO3 models
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Warming for the Long Haul
1000 10,000 years years from now from
now 2000 Gton C 3 C 1.5 5000 Gton C 5 3
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How much is 3 C?
3 C
Northern Hemisphere Average Temperature
1000
2000
Year A.D.
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So What Part I Sea Level
Pliocene3 Myr ago
Sea Level, m
100
Eocene
40
Myr
ago
50
Global T Change, C
Today
-10
-5
0
5
-50
-100
Last Glacial
Maximum
20
kyr
ago
-150
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So What Part I Sea Level
Pliocene3 Myr ago
Sea Level, m
100
Eocene
40
Myr
ago
50
IPCC Forecast for the year 2100
Global T Change, C
Today
-10
-5
0
5
-50
-100
Last Glacial
Maximum
20
kyr
ago
-150
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So What Part I Sea Level
Pliocene3 Myr ago
Sea Level, m
100
Eocene
40
Myr
ago
50
Eventual Sea Level Rise?
Global T Change, C
Today
-10
-5
0
5
-50
-100
Last Glacial
Maximum
20
kyr
ago
-150
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Message to Florida 20 meters would be it for
yall
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Ice sheet models
It takes thousands of years to respondto
climate changes.
Ice flows if theres water at the bed
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Real ice sheets
The real Greenlandice sheet responds in a few
months.
Melt water carries
heat quickly
We dont know how water gets through the ice
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Zwalley et al (2002)
A moulin in Greenlandwhere water submerges into
the ice.
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Earthquakes under Greenland ice
Ekstrom et al., 2006
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Heinrich Events 30-70 kyr ago
Ice sheet collapsed into the ocean
Raised sea level 5 min a few centuries. Could
the Greenland ice sheet start doing this?
Ice Rafted Debris (layers of rocks inocean
sediments)
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Meltwater Pulse 1A 14 kyr ago
1.5 to 3 Greenlandsin 1-5 centuries.Were not
even surewhere this water came from.
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A long-term sea level scenario
5000 Gton of C release (business-as-usual to
2100 then stop)50 m sea level rise,
eventually 3.5 of the land area, home to
gt10 of the worlds population Every American
ultimately inundates 1000 sq. ft. of land per
year.
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The Next Ice Age
Precession Cycle
Intense Seasons
in the
Southern Hemisphere
n
Intense Seasons
o
i
s
s
in the
e
c
e
r
Northern Hemisphere
P

k
a
e
Obliquity Cycle
W
25
24
Angle
from the Pole
23
to the Orbit
22
y
Eccentricity Cycle
t
i
c
5 Elliptical,
i
r
t
n
95 Circular
e
c
c
E

w
o
L
100 Circular
300
200
100
0
Thousands of Years Ago
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A Threshold Model
sunlight
Interglacial Climate State
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A Threshold Model
summer sunlight gets weak
Interglacial Climate State
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A Threshold Model
summer sunlight gets weak
winter snow survives the summeran ice sheet is
born
Glacial Climate State
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A Threshold Model
sunlight gets strong again
Ice reflects light back to space
ice persists
Glacial Climate State
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Dim Northern Hemisphere Sun Growing Ice
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CLIMBER Model Nucleates an Ice Sheet
Trigger
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CLIMBER model, Archer and Ganopolski, 2005
Critical Insolation Value, W/m2
If CO2 is higher,it takes a colder sunto
nucleate the ice sheet.
Atmospheric pCO2
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Archer and Ganopolski, 2005
Natural Near miss! Wait until50 kyr
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1000 Gton Wait until130 kyr fromnow
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5000 Gton No glaciationfor 400 kyr
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Conclusions
Global warming is well understood, it has been
detected,and the forecast for the end of the
century is frightening. CO2 emission will
continue to effect climate for hundredsof
thousands of years into the future. Sea level
may ultimately rise 100 times more than the
forecast for the year 2100.