N2O-Climate feedback

P.Friedlingstein, L. Bopp, S. Zaehle,

P. Cadule and A. Friend

IPSL/LSCE

Climate carbon cycle feedback

Positivefeedback

11 coupled climate carbon cycle models, same forcing in emissions, two simulations.

Largerclimate change

Radiative forcing

Climate - Biogeochemical cycle feedback ?

: Anthropogenic but also Natural sources/sinks

Feedback estimate

• What are the feedbacks between climate and other major radiatively active BGCs

• Which ones have to be calculated online-0.4

-0.2

0

0.2

0.4

CO2 CH4 N2O

? ?

Climate-BGC gain

Atmospheric [N2O] *

IPCC, TAR, 2001(*) In the following, whenever I say CO2, I mean N2O

N2O Emissions

IPCC, TAR, 2001

N2O

• What are the potential changes in natural N2O emissions due to climate change

Methodology

• Estimate land and ocean N2O emissions

– Historical and Future evolution (SRES-A2)– Use of IPSL AOGCM climate fields to drive

• ORCHIDEE land BGC model• PISCES ocean BGC model

• Estimate atmospheric change due to climate-N2O emission feedback

Experimental design

• Landa) CO2 forcing only

b) CO2 and climate change forcing

No changes in land-use, fertilizer use, Nitrogen deposition,…

Ocean

CO2 and climate change forcing

Climate forcing

ORCHIDEE

Krinner et al., 2005Zaehle et al., 2006

Some validation

PS Sönke will buy more validation data at any price !

PISCES

PO43-

Diatoms

MicroZoo

P.O.M.

D.O.M

Si

FeNano-phyto

Meso Zoo

NO3-

NH4+

Small Large

N2O Parametrization from Suntharalingham et al., 2002

J_N2O = f(O2 consumption, O2 concentration)

Aumont et al., 2003

PISCES Model

N2O Flux mgN/m2/yr

ObservationsNevison et al. 2005 :

Ocean validation

Atlantic

East Pacific

West Pacific

Indian

Ocean validation

Atmospheric pCO2 (ppm)

Primary Productivity (GtC/yr)

N2O Flux (TgN/yr)

Ocean story

Change inO2 concentration (mol/l)

Change inN2O flux (mgN/m2/yr)

2100 - 1860

Ocean story

Land story

N2O Flux (TgN/yr)

Land story

Change inN2O flux (gN/m2/yr)

2100 - 1860

Grassland and cropland

Forests

Grassland and cropland

Forests

Most of the change occurs in temperate

grasslands and croplands

Land story

Relative change inN2O flux (%)

2100 - 1860

Grassland and cropland

ForestsWorldwide increase

Atmospheric N2O Budget

ATM

ONEMI

t

ON

22

ON2

EMIWhere

ATM

is the change in atmosphericN2O concentration since PI.

is the change in natural emissions since PI

is the life-time of N2O in the atmosphere

ocean

land

sink

source

10 ppb decrease -0.03 W/m2

Atmospheric N2O BudgetEmissions

Atm. Source/Sink

Atm. Concentration

EMI

EMI

5.5

3.5

1.5T

gN/y

r

0.

-0.2

ppb

275

270

265

ppb

But… key role of N inputs

Conclusions

• Climate change alone may induces– decrease of oceanic emissions– increase of continental emissions

• Overall effect : negative feedback– Small (10 ppb decrease) relative to future

anthropogenic scenarios (+ 200 ppb)

• Future continental emissions largely driven by N dep, Nfert.

• However …

N2O G-IG changes

Positive feedback !!!

Last slide

Did we just prove the ice core wrong ?

SRESA2 – IPSLCM2 - NPZD SRESA2 – IPSLCM4 -PISCES

Observations from Levitus(mol/l)

PISCES Model(mol/l)

02 distribution

Climate forcing

Land story

Change inN2O flux (gN/m2/yr)

2100 - 1860

Most of the change occurs in temperate

grasslands and croplands

CO2 alone

Climate and CO2

Climate effect