Status of the carbon cycle to be incorporated in aogcms
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Status of the Carbon Cycle to be incorporated in AOGCMs. Peter Cox & Pierre Friedlingstein. Outline. INTRODUCTION : Rationale for including the carbon cycle in AOGCMs : Carbon-Cycle Climate Interactions. CURRENT STATUS OF CARBON CYCLE IN AOGCMs:

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Status of the carbon cycle to be incorporated in aogcms

Status of the Carbon Cycle to be incorporated in AOGCMs

Peter Cox

&

Pierre Friedlingstein


Status of the carbon cycle to be incorporated in aogcms

Outline

INTRODUCTION :

  • 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


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.

The Carbon Cycle and Climate Change

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)


The carbon cycle and climate change1

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.

The Carbon Cycle and Climate Change


Status of the carbon cycle to be incorporated in aogcms

Temperature

Carbon Cycle-Climate Coupling

The Example of the Glacial Cycles

CO2

Vostok Ice Core Records

showing strong correlations

between Temperature and

Carbon Dioxide over

the last 400,000 years


Status of the carbon cycle to be incorporated in aogcms

CO2 Concentration (measured at Mauna Loa on Hawaii)

Atmospheric CO2 is increasing

at about half the rate of emissions

Seasonal cycle is due

to the land biosphere


Status of the carbon cycle to be incorporated in aogcms

Year-to-Year Variability in CO2 Growth-rate is driven by

Climatic Anomalies (e.g. El Nino, Volcanoes)


Status of the carbon cycle to be incorporated in aogcms

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 ??


Status of the carbon cycle to be incorporated in aogcms

CO2 Growth-Rate is Sensitive to Climatic Anomalies…..

2003 Anomaly

Total

Fossil Fuels

Years after

Volcanic Eruptions

Land-use Change

Mt Agung

El Chichon

Pinatubo


The carbon cycle and climate change2

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.

The Carbon Cycle and Climate Change


The carbon cycle and climate change3

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?

The Carbon Cycle and Climate Change


Status of carbon cycle in tar aogcms

Status of Carbon Cycle in TAR AOGCMs

Online

CLIMATE

Offline

Greenhouse

Effect

CO2

CO2 Uptake by Ocean / CO2 buffering effect

CO2 Uptake by Land / CO2-fertilization of plant growth

OCEAN

LAND

Fossil Fuel + Net Land-use

CO2 Emissions


Status of carbon cycle in ar4 aogcms c 4 mip

Status of Carbon Cycle in AR4 AOGCMs (C4MIP)

Online

CLIMATE

Offline

Greenhouse

Effect

Climate Change effects on

Solubility of CO2

Vertical Mixing

Circulation

Climate Change effects on plant productivity, soil respiration

CO2

OCEAN

LAND

Fossil Fuel + Net Land-use

CO2 Emissions


Status of the carbon cycle to be incorporated in aogcms

Hadley Centre climate-carbon GCM simulation shows climate change suppressing land carbon uptake…..


Coupled climate carbon cycle intercomparison project c 4 mip

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 

Coupled Climate Carbon Cycle Intercomparison Project (C4MIP)


Status of the carbon cycle to be incorporated in aogcms

C4MIP Models – extra CO2 due to climate effects on the carbon cycle

All models simulate a positive feedback, but with very different magnitudes.


Status of the carbon cycle to be incorporated in aogcms

Change in CO2 Emissions Partitioning in C4MIP Models

Positive Carbon

Cycle Feedback


Status of the carbon cycle to be incorporated in aogcms

C4MIP Models indicate that Climate Change will hinder CO2 uptake by the land, but the size of this effect is uncertain


C 4 mip robust results and uncertainties

All C4MIP models simulate a positive feedback

larger warming

or larger reduction in emissions

C4MIP: Robust Results and Uncertainties


Status of the carbon cycle to be incorporated in aogcms

GlobalEmissions for Climate Stabilisation

2000

2050

~ 8 GtC/yr in 2000

~ 3 GtC/yr by 2050


Status of the carbon cycle to be incorporated in aogcms

Impact of Climate-Carbon Cycle Feedbacks on Integrated Permissible Emissions

Impact of Carbon

Cycle Feedbacks

Single model: urgently need to provide updated stabilisation permissible emissions scenarios with error bars covering full climate-carbon system!


C 4 mip robust results and uncertainties1

All C4MIP models simulate a positive feedback

larger warming

or 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

C4MIP: Robust Results and Uncertainties


Contributions to uncertainty in future co 2 concentration from c 4 mip models

Contributions to uncertainty in future CO2 concentration (from C4MIP models)

IPCC, AR4


C 4 mip 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.

C4MIP: Key Uncertainties in Climate-Carbon Feedback


Status of the carbon cycle to be incorporated in aogcms

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.


Land use

Land use


Status of the carbon cycle to be incorporated in aogcms

Statistical Dynamics approach to large-scale Vegetation Dynamics

Including age-class distributions

Explicit simulation of rainforest regrowth

on multiple patches

Moment Equations for

Statistics of Vegetation State

Morecroft et al., 2001


Interactive forest fire

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


Status of the carbon cycle to be incorporated in aogcms

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.


Examples of ar5 ocean ecosystem model pisces

PO43-

Diatoms

NH4+

Si

Nano-phyto

NO3-

Iron

MicroZoo

D.O.M

Meso Zoo

P.O.M

Small Ones

Big Ones

Examples of AR5 Ocean Ecosystem Model (PISCES)

Aumont et al., 2003


Status of the carbon cycle to be incorporated in aogcms

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.


Nitrogen deposition is already significant and will increase

Nitrogen Deposition is already significant and will increase

Millennium Ecosystem Assessment, 2005


Status of the carbon cycle to be incorporated in aogcms

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 ?


Status of carbon cycle in tar aogcms1

Status of Carbon Cycle in TAR AOGCMs

Online

CLIMATE

Offline

Greenhouse

Effect

CO2

CO2 Uptake by Ocean / CO2 buffering effect

CO2 Uptake by Land / CO2-fertilization of plant growth

OCEAN

LAND

Fossil Fuel + Net Land-use

CO2 Emissions


Status of carbon cycle in ar4 aogcms c 4 mip1

Status of Carbon Cycle in AR4 AOGCMs (C4MIP)

Online

CLIMATE

Offline

Greenhouse

Effect

Climate Change effects on

Solubility of CO2

Vertical Mixing

Circulation

Climate Change effects on plant productivity, soil respiration

CO2

OCEAN

LAND

Fossil Fuel + Net Land-use

CO2 Emissions


Possible status of carbon cycle in ar5 aogcms

Possible Status of Carbon Cycle in AR5 AOGCMs

Online

CLIMATE

Offline

Greenhouse

Effect

Climate Change effects on

Solubility of CO2

Vertical Mixing

Circulation

& Ocean Ecosystem Structure

Climate Change effects on plant productivity, soil respiration

& Fires

CO2

Riverine CO2

fluxes

OCEAN

LAND

Iron Dust

Deposition

Fossil Fuel

CO2 Emissions

Land-use

Change

N and O3

Deposition


Status of the carbon cycle to be incorporated in aogcms

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.


Status of the carbon cycle to be incorporated in aogcms

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.


Status of the carbon cycle to be incorporated in aogcms

THE END !


Loop the new ipsl c c model

Climate

Atmospheric

[CO2]

AtmosphereLMDZ4

OceanORCA-LIMOPA 8.2

Coupler

OASIS 2.4

∆t = physic time step

∆t = 1day

CO2 concentrationre-calculated each month

MarineBiochemistry

PISCES

Terrestrial biosphereORCHIDEE(STOMATE activated)

Carbon

Land flux GtC/mth

Ocean flux GtC/mth

EMI = external forcing

[Marland et al, 2005

Houghton, 2002]

Net total carbon flux Fluxland + Fluxocean

LOOP The new IPSL C-C model

Cadule et al., in prep


Zero order validation

Global mean surface temperature anomalies

Base period : 1961-1990

Zero Order Validation

Cadule et al., in prep


First order validation

fossil fuel

Atmospheric carbon variation

land

Land use

ocean

First Order Validation

  • “IPCC” carbon budget (GtC/yr)

1990’s

1980’s

Atm

Ocean

Land

Cadule et al., in prep


Second order validation

Second Order Validation

  • Atmospheric CO2

    • Offline transport over 1979-2003

Cadule et al., in prep


Status of the carbon cycle to be incorporated in aogcms

  • Seasonal cycle

  • Long term trend

Cadule et al., in prep


A climate response to co 2

aclimate response to CO2

Friedlingstein et al., 2006

IPSL-CM2_C

IPSL_CM4_LOOP


B c cycle response to co 2

bC-cycle response to CO2

LAND

OCEAN

Friedlingstein et al., 2006

IPSL-CM2_C

IPSL_CM4_LOOP


G c cycle response to climate

gC-cycle response to climate

LAND

OCEAN

Friedlingstein et al., 2006

IPSL-CM2_C

IPSL_CM4_LOOP


Why such a large uncertainty in the land carbon response to climate

Why such a large uncertainty in the Land Carbon Response to Climate ?


Status of the carbon cycle to be incorporated in aogcms

IPSL-CM2_C

IPSL_CM4_LOOP

HadCM3C

REGIONAL LAND RESPONSE TO CLIMATE


Improving the carbon cycle

Improving the carbon cycle

  • Coupled C-C run with fires and land-use

  • Include nitrogen cycle


Nitrogen

Nitrogen

Motivation:

  • Controls the carbon cycle

    • Impact on carbon uptake

    • Impact on the C-C feedback estimate


Examples of ar5 carbon cycle models orchidee and pisces

PO43-

Diatoms

NH4+

Si

Nano-phyto

NO3-

Iron

MicroZoo

D.O.M

Meso Zoo

P.O.M

Small Ones

Big Ones

Examples of AR5 carbon cycle models (ORCHIDEE and PISCES)

Aumont et al., 2003

Krinner et al., 2005


The land response ipsl

The land response - IPSL

Increase in

soil aridity

Extension of the growing season

Berthelot et al., 2002


Status of the carbon cycle to be incorporated in aogcms

Climate-Land Feedbacks and Forcings

Anthropogenic

Emissions

Climate Sensitivity

+

CO2

Temp

Climate

Sensitivity of Soil respiration to Temp

-

+

_

NPP

Decomp

Land

N mineralisation

+

+

The Key missing negative feedback – increased N availability in a warmer world ?

Avail N

Chemistry

Anthropogenic

N deposition


Status of the carbon cycle to be incorporated in aogcms

Climate-Land Feedbacks and Forcings

Anthropogenic

Emissions

Climate Sensitivity

+

CO2

Temp

Climate

-

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?

NPP

Land

-

Trop O3

Anthropogenic

Emissions


Status of the carbon cycle to be incorporated in aogcms

Climate-Land Feedbacks and Forcings

Anthropogenic

Emissions

Regional Climate

Change

Climate Sensitivity

?

+

CO2

Precip

Temp

Climate

+

CO2

Fertilisation

Sensitivity of Soil respiration to Temp

+

-

+

+

+

+

_

+

Surface Energy

Balance

_

Veg

Cover

+

NPP

Decomp

Land

Land-use

Change

N mineralisation

-

+

+

Avail N

Chemistry

Trop O3

Anthropogenic

Emissions

Anthropogenic

N deposition


Status of the carbon cycle to be incorporated in aogcms

Increased Tropospheric O3 and Vegetation –

Feedbacks from biogenic emissions

+

CO2

Precip

Temp

Isoprene emissions increase with temperature

Veg

Cover

NPP

Decomp

+

+

Isoprene emissions increase with increasing vegetation cover?

+

Trop O3

Isoprene

Isoprene increases O3 in high NOx conditions

Anthropogenic

NOx emissions


Humans now dominate the global nitrogen cycle

Humans now dominate the Global Nitrogen Cycle

Millennium Ecosystem Assessment, 2005


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