Status of the Carbon Cycle to be incorporated in AOGCMs
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![Page 1: Status of the Carbon Cycle to be incorporated in AOGCMs](https://reader036.fdocuments.net/reader036/viewer/2022070402/568138a8550346895da06843/html5/thumbnails/1.jpg)
Peter Cox &
Pierre Friedlingstein
Status of the Carbon Cycle to be
incorporated in AOGCMs
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OutlineINTRODUCTION : Rationale for including the carbon cycle in AOGCMs : Carbon-Cycle Climate
Interactions.
CURRENT STATUS OF CARBON CYCLE IN AOGCMs: Coupled-Climate Carbon Cycle Model Intercomparison Project (C4MIP). Robust findings and key uncertainties. Missing processes.
POSSIBLE STATUS OF CARBON CYCLE IN AOGCMS BY AR5: Modelling of CO2 emissions from land-use and land-management. More detailed ocean ecosystem models Interactive nitrogen cycling on land. Links to changes in atmospheric chemistry and aerosols ? Implications for AR5 scenarios.
CONCLUSIONS
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The Carbon Cycle and Climate Change
Currently only about half of human emissions of CO2 remain in the atmosphere - the ocean and land ecosystems appear to be absorbing the remainder.
Atmospheric Increase = 3.2 +/- 0.1 GtC/yr (50%)
Emissions (fossil fuel, cement) = 6.4 +/- 0.4 GtC/yr (100%)
Ocean-atmosphere flux = -1.7 +/- 0.5 GtC/yr (27%)
Land-atmosphere flux = -1.4 +/- 0.7 GtC/yr (22%)
Estimated Global Carbon Balance for 1990s (IPCC TAR)
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The Carbon Cycle and Climate Change
Currently only about half of human emissions of CO2 remain in the atmosphere - the ocean and land ecosystems appear to be absorbing the remainder.
Atmosphere-land and atmosphere-ocean fluxes of CO2 are sensitive to climate.
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Temperature
CO2
Vostok Ice Core Recordsshowing strong correlations between Temperature and
Carbon Dioxide overthe last 400,000 years
Carbon Cycle-Climate Coupling
The Example of the Glacial Cycles
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CO2 Concentration (measured at Mauna Loa on Hawaii)
Atmospheric CO2 is increasingat about half the rate of emissions
Seasonal cycle is dueto the land biosphere
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Year-to-Year Variability in CO2 Growth-rate is driven byClimatic Anomalies (e.g. El Nino, Volcanoes)
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CO2 growth-rate anomalies are normally well correlated with El Nino (+ve anomalies) and
La Nina (-ve anomalies)
…… except after major volcanoes…
…..or in the last few years ??
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CO2 Growth-Rate is Sensitive to Climatic Anomalies…..
Fossil Fuels
Total
Land-use Change
2003 Anomaly
Years after Volcanic Eruptions
El ChichonPinatubo
Mt Agung
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The Carbon Cycle and Climate Change
Currently only about half of human emissions of CO2 remain in the atmosphere - the ocean and land ecosystems appear to be absorbing the remainder.
Atmosphere-land and atmosphere-ocean fluxes of CO2 are sensitive to climate.
To date most GCMs have used prescribed atmospheric CO2 and therefore neglect climate-carbon cycle feedbacks.
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The Carbon Cycle and Climate Change
Currently only about half of human emissions of CO2 remain in the atmosphere - the ocean and land ecosystems appear to be absorbing the remainder.
Atmosphere-land and atmosphere-ocean fluxes of CO2 are sensitive to climate.
Most GCMs prescribe atmospheric CO2 and therefore neglect climate-carbon cycle feedbacks.
How important might these be for future climate change?
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Status of Carbon Cycle in TAR AOGCMs
Fossil Fuel + Net Land-use
CO2 Emissions
Online
OfflineCLIMATE
OCEAN LAND
CO2
Greenhouse Effect
CO2 Uptake by Land / CO2-fertilization of plant
growth
CO2 Uptake by Ocean / CO2 buffering effect
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Status of Carbon Cycle in AR4 AOGCMs (C4MIP)
Fossil Fuel + Net Land-use
CO2 Emissions
Online
OfflineCLIMATE
OCEAN LAND
CO2
Greenhouse EffectClimate Change effects on
Solubility of CO2
Vertical MixingCirculation
Climate Change effects on plant productivity, soil
respiration
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Hadley Centre climate-carbon GCM simulation shows climate change suppressing land carbon uptake…..
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Coupled Climate Carbon Cycle Intercomparison Project (C4MIP)
• IGBP/GAIM (AIMES) - WCRP/WGCM coordinated activity to explore the coupled climate carbon cycle feedback
• 11 Coupled Climate-Carbon models (7 AOGCMs) have now been used to simulate 21st century climate and CO2 under similar scenarios.
• Models agree that effects of climate change on the carbon cycle will lead to more CO2 in the atmosphere (positive climate-carbon cycle feedback).
• But magnitude of this effect, and primary cause, vary between models
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C4MIP Models – extra CO2 due to climate effects on the carbon cycle
All models simulate a positive feedback, but with very different magnitudes.
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Positive CarbonCycle Feedback
Change in CO2 Emissions Partitioning in C4MIP Models
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Fraction of Emissions Absorbed by the Land (1860-2100)
0
0.1
0.2
0.3
0.4
0.5
0.6
HadCM3LCIPSL-CM2C
CSM-1MPI LLNL
FRCGCUMD
UVic-2.7CLIMBERBERN-CC
Uncoupled Coupled
C4MIP Models indicate that Climate Change will hinder CO2 uptake by the land, but the size of this effect is uncertain
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C4MIP: Robust Results and Uncertainties
All C4MIP models simulate a positive feedback larger warmingor larger reduction in emissions
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Global Emissions for Climate Stabilisation
20502000
~ 8 GtC/yr in 2000
~ 3 GtC/yr by 2050
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Impact of CarbonCycle Feedbacks
Single model: urgently need to provide updated stabilisation permissible emissions scenarios with error bars covering full climate-carbon system!
Impact of Climate-Carbon Cycle Feedbacks on Integrated Permissible Emissions
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C4MIP: Robust Results and Uncertainties
All C4MIP models simulate a positive feedback larger warmingor larger reduction in emissions
Uncertainty in the 21st century CO2 (range: 750 – 1000 ppm)
Large uncertainty on the feedback (20 to 220 ppm)
Feedback analysis to attribute uncertainty
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Contributions to uncertainty in future CO2 concentration (from C4MIP models)
IPCC, AR4
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C4MIP: Key Uncertainties in Climate-Carbon Feedback
Response of land NPP to climate (includes uncertainties in hydrological changes)
Transient climate sensitivity to CO2
Response of soil (heterotrophic) respiration to climate.
However, rate of increase of CO2 also depends on responses of land and especially ocean uptake to CO2.
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Possible Status of Carbon Cycle in AOGCMs by AR5
More complete model validation/use of observational constraints.
Modelling of CO2 emissions from land-use and land-management and forest fires.
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Land use
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Explicit simulation of rainforest regrowth on multiple patches
Moment Equations for Statistics of Vegetation State
Morecroft et al., 2001
Statistical Dynamics approach to large-scale Vegetation Dynamics Including age-class distributions
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Interactive Forest Fire
• Currently implemented in ORCHIDEE– will allow to estimate
role of fire on CO2
– will allow to estimate impact of climate change on fire and feedback on climate
– Emissions of CH4, NOx,…
Thonicke, et al., 2005
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Possible Status of Carbon Cycle in AOGCMs by AR5
More complete model validation/use of observational constraints.
Modelling of CO2 emissions from land-use and land-management and forest fires.
More detailed ocean ecosystem models.
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Examples of AR5 Ocean Ecosystem Model (PISCES)
PO43-
Diatoms
MicroZoo
P.O.M
D.O.M
Si
IronNano-phyto
Meso Zoo
NO3-
NH4+
Small Ones Big Ones
Aumont et al., 2003
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Possible Status of Carbon Cycle in AOGCMs by AR5
More complete model validation/use of observational constraints.
Modelling of CO2 emissions from land-use and land-management and forest fires.
More detailed ocean ecosystem models.
Interactive nitrogen cycling on land.
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Nitrogen Deposition is already significant and will increase
Millennium Ecosystem Assessment, 2005
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Possible Status of Carbon Cycle in AOGCMs by AR5
More complete model validation/use of observational constraints.
Modelling of CO2 emissions from land-use and land-management and forest fires.
More detailed ocean ecosystem models.
Interactive nitrogen cycling on land.
Links to changes in atmospheric chemistry and aerosols ?
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Status of Carbon Cycle in TAR AOGCMs
Fossil Fuel + Net Land-use
CO2 Emissions
Online
OfflineCLIMATE
OCEAN LAND
CO2
Greenhouse Effect
CO2 Uptake by Land / CO2-fertilization of plant
growth
CO2 Uptake by Ocean / CO2 buffering effect
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Status of Carbon Cycle in AR4 AOGCMs (C4MIP)
Fossil Fuel + Net Land-use
CO2 Emissions
Online
OfflineCLIMATE
OCEAN LAND
CO2
Greenhouse EffectClimate Change effects on
Solubility of CO2
Vertical MixingCirculation
Climate Change effects on plant productivity, soil
respiration
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Possible Status of Carbon Cycle in AR5 AOGCMs
Fossil FuelCO2 Emissions
Online
OfflineCLIMATE
OCEAN LAND
CO2
Greenhouse Effect
Land-useChange
Iron DustDeposition
N and O3Deposition
Climate Change effects onSolubility of CO2
Vertical MixingCirculation
& Ocean Ecosystem Structure
Climate Change effects on plant productivity, soil
respiration & Fires
Riverine CO2 fluxes
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Conclusions I
Climate and carbon cycle are tightly coupled, so the carbon cycle must be part of Earth System Models.
First generation coupled-climate carbon cycle models all suggest that climate change will increase the fraction of CO2 emissions that are airborne.
There are major uncertainties in the size of this positive climate-carbon feedback (leading to an extra 20-200ppmv by 2100 under the A2 emissions scenario, with a mean of 90+/-50 ppmv).
This uncertainty also impacts on the CO2 emissions consistent with stabilisation at a given concentration.
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Conclusions 2
By AR5 climate-carbon cycle models are likely to include a number of processes that were missing in the first generation C4MIP models, including:
Interactive calculation of net land-use emissions. More complex ocean ecosystem models. Interactive N-cycling on the land. Riverive carbon fluxes from land to ocean
This places new demands on driving scenarios that need to include consistent land-use change/management, N-deposition, near surface O3 concentration, dust inputs to the ocean.
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THE END !
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LOOP The new IPSL C-C model
Net total carbon flux Fluxland + Fluxocean
[ ] ( )12.2
2 oceanland FluxFluxEMI
dt
COd −−=
Terrestrial biosphereORCHIDEE
(STOMATE activated)
MarineBiochemistry
PISCES
OceanORCA-LIM
OPA 8.2
AtmosphereLMDZ4
EMI = external forcing[Marland et al, 2005
Houghton, 2002]
Ocean flux GtC/mthLand flux GtC/mth
CouplerOASIS 2.4
ClimateAtmospheric[CO2]
CO2 concentration
re-calculated each month
∆t = 1day
Carbon
∆t = physic time step
Cadule et al., in prep
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Zero Order Validation
Cadule et al., in prep
Global mean surface temperature anomalies
Base period : 1961-1990
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First Order Validation• “IPCC” carbon budget (GtC/yr)
LOOP IPCC LOOP IPCC
2.7 3.3 3.3 3.2
2.0 1.8±0.8 2.0 2.2±0.4
2.8 1.6
(-0.3 to 4)
3.3 2.6
(1 to 4.3)
1980’s 1990’s
Atm
Ocean
Land
Cadule et al., in prep
Atmospheric carbon variation
Land use fossil fuel land
ocean
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Second Order Validation
• Atmospheric CO2 – Offline transport over 1979-2003
Cadule et al., in prep
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Cadule et al., in prep
• Seasonal cycle
• Long term trend
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climate response to CO2
Friedlingstein et al., 2006IPSL-CM2_C IPSL_CM4_LOOP
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C-cycle response to CO2
OCEAN
LAND
Friedlingstein et al., 2006IPSL-CM2_C IPSL_CM4_LOOP
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C-cycle response to climate
OCEAN
LAND
Friedlingstein et al., 2006IPSL-CM2_C IPSL_CM4_LOOP
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Why such a large uncertainty in the Land Carbon
Response to Climate ?
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IPSL-CM2_C IPSL_CM4_LOOP HadCM3C
REGIONAL LAND RESPONSE TO CLIMATE
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Improving the carbon cycle
• Coupled C-C run with fires and land-use
• Include nitrogen cycle
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Nitrogen
Motivation:
• Controls the carbon cycle– Impact on carbon uptake– Impact on the C-C feedback estimate
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Examples of AR5 carbon cycle models (ORCHIDEE and PISCES)
PO43-
Diatoms
MicroZoo
P.O.M
D.O.M
Si
IronNano-phyto
Meso Zoo
NO3-
NH4+
Small Ones Big Ones
Aumont et al., 2003Krinner et al., 2005
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The land response - IPSL
Extension of the growing
season
Increase insoil aridity
Berthelot et al., 2002
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CO2 Temp
NPP Decomp
+Climate Sensitivity
Sensitivity of Soil respiration to Temp
+-
AnthropogenicEmissions
Avail N
N mineralisation
++
AnthropogenicN deposition
_
Climate
Land
Chemistry
Climate-Land Feedbacks and Forcings
The Key missing negative feedback – increased N availability in a warmer world ?
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CO2 Temp
NPP
+Climate Sensitivity
-
AnthropogenicEmissions
Climate
Land
Climate-Land Feedbacks and Forcings
Anthropogenic Emissions
Trop O3
-
The Key missing forcing factor?
Tropospheric O3 levels are projected to increase significantly - to levels which may be detrimental to plants (see for example Gregg et al., 2003)
Could this suppress the land carbon sink and accelerate global warming?
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CO2 TempPrecip
Veg Cover
NPP Decomp
+Climate Sensitivity
Sensitivity of Soil respiration to Temp
++
+
_+ -CO2
Fertilisation
AnthropogenicEmissions
Climate-Land Feedbacks and Forcings
Surface EnergyBalance
++
Regional Climate Change
?
+
+
Land-useChange
Avail N
N mineralisation
++
AnthropogenicN deposition
Anthropogenic Emissions
Trop O3
-
_
Climate
Land
Chemistry
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CO2 TempPrecip
Veg Cover
NPP Decomp
+
AnthropogenicNOx emissions
Increased Tropospheric O3 and Vegetation – Feedbacks from biogenic emissions
Trop O3 Isoprene
+
Isoprene emissions increase with temperature
+
Isoprene increases O3 in high NOx conditions
+Isoprene emissions increase with increasing vegetation cover?
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Humans now dominate the Global Nitrogen Cycle
Millennium Ecosystem Assessment, 2005
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