can we infer climate-carbon cycle feedback from past records?
DESCRIPTION
Can we infer climate-carbon cycle feedback from past records?. P. Friedlingstein and IC Prentice Paris/Bristol/Exeter/Sidney + inputs from V. Masson-Delmotte. The magnitude of the problem. 830 ppm. Uncertainty due to the carbon cycle uncertainty. 730 – 1000 ppm. - PowerPoint PPT PresentationTRANSCRIPT
P. Friedlingstein and IC PrenticeParis/Bristol/Exeter/Sidney
+ inputs from V. Masson-Delmotte
The magnitude of the problem
Brussels, May. 27th 2009
Uncertainty due to the carbon cycle uncertainty
2.6 – 4.1 °C2.4 – 5.6 °C
830 ppm
730 – 1000 ppm
Higher [CO2], larger climate change
IPCC, 2007
Climate-Carbon Cycle FeedbackCO2 = EMI - Fao - Fab (1) T = CO2 + Tind (2)with: Fao = ao CO2 +ao T (3) Fab = ab CO2 +ab T (4)
(3) and (4) in (1), then (1) in (2) gives:
T = 1/(1-g) Tunc
with:g = (ao + ab )/(1+ ao + ab)
Climate-Carbon Cycle FeedbackT = 1/(1-g) Tunc = f Tunc
g = (ao + ab )/(1+ ao + ab)
g is the gain of the climate-carbon cycle feedback
f = 1/(1-g) f is the feedback factor
and is the carbon cycle sensitivity to climate (C/T)
Climate-Carbon Cycle Feedback
Carbon cycle sensitivity
to climate
gClimate carbon cycle
gain
0.04 – 0.30
30 – 200 GtC/K
What are the available observations ?
Glacial interglacial CO2 – Temperature
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g =ΔT
ΔCO2
×ΔCO2
ΔT
Climate sensitivity is estimated here from 2xCO2 GCMs estimates,in the absence of physical feedbacks (black body response only).
Two caveats
Glacial interglacial CO2 – Temperature
1. Physical feedbacks
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g =ΔT
ΔCO2
×ΔCO2
ΔT
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g = α ×γ
1+ β
Torn and Harte, 2006
Friedlingstein et al., 2006
is the climate sensitivity, accounting for all physical feedbacks
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TTH 06 =ΔF
λ BB
λ BB = 3.8Wm−2K −1
ΔTF 06 =ΔF
λ i∑λ i∑ =1.3 ± 0.3Wm−2K −1
gG-IG= 0.04*3.8/1.3= 0.12
Using the Full EPICA record
Glacial interglacial CO2 – Temperature
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CO2
ΔT= 7.8633 ppm/K and taking from AR4 gG-IG= 0.08
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T
ΔCO2
2. Does this help for future projections?
Last Millennium and LIA
Last Millennium and LIA
dCO2/dT= 50.6 ppm/K dCO2/dT= 39.9 ppm/K
Last Millennium and LIA
Last Millennium and LIA
dCO2/dT= 7.7 [ 1.7 – 21.4] ppm/K
Confusion in terminology …
dCO2/dT is neither g no …
Last Millennium and LIA
dCO2/dT= 7.7 [ 1.7 – 21.4] ppm/K
One could derive the gain g:(again, taking dT/dCO2
from 2xCO2 sensitivity)
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gLIA = 7.7 ×3[2 to 4.5]
286= 0.08 [0.05 to 0.12]
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T
biosphere
Ocean
€
CO2 = γΔT − βΔCO2
i.e.
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CO2
ΔT=
γ
1+ β
€
Cout = γΔT
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CO2
time
€
Cin = βΔC
Last Millennium and LIAOr one could derive
But one needs to know on millenium time scales …
Interannual variability of CO2G
t. C
per
yea
rS
OI
1955 1960 1965 1970 1975 19851980 1990 1995 2000
8
6
4
2
30
0
-30
CO2 Annual Growth Rate
Interannual variability of CO2
dCO2/dT= 2.9 ppm/K
= -90 GtC/K gG-IG= 0.03
Summary
gain Carbon sensitivity to climate (GtC/K)
G-IG 0.08 ≈ -110*
LIA 0.08 ≈ -110*
IAV 0.03** -90
C4MIP models average
0.15 -109
*assuming ≈ 5.5, i.e. AF≈ 0.15**assuming equilibrium response
Palaeo and historical CO2 variability could help to constraintClimate carbon cycle feedbackEstimate of seems to be more robust than g across timescales
SummaryPalaeo and historical CO2 variability might help
to constrain Climate carbon cycle feedbackHowever, large uncertainties on data and on
use of dataEstimate of seems to be more robust than g
across timescales. Is this accidental ?Do we get the “right” number for the right
reason (right process) ?Best way is certainly not what I just
presented...
We should simulate the past rather thanplay with past data to infer future response