Is possible to constrain models climate sensitivity using paleo proxy-data ? Hugues Goosse, Marie-France Loutre, Thierry Fichefet, Université catholique.

Is possible to constrain models climate sensitivity using paleo

proxy-data ?

Hugues Goosse, Marie-France Loutre, Thierry Fichefet,

Université catholique de Louvain, Belgium

Jesus Fidel Gonzalez-Rouco, Universidad Complutense de Madrid, Spain

Hugo Beltrami, Environmental Sciences Research Centre, Nova Scotia, Canada

Description of LOVECLIM

LOVECLIM (3D)

ECBilt(atmosphere)

AGISM(ice sheets)

CLIO(sea ice-ocean)

VECODE(terr. biosphere)

LOCH(oceanic carbon cycle)

ECBilt (Opsteegh et al., 1998)Quasi-geostrophic atmospheric model (prescribed cloudiness; T21, L3).

CLIO (Goosse and Fichefet, 1999)Ocean general circulation model coupled to a thermodynamic-dynamic sea ice model (3 x 3, L20).

VECODE (Brovkin et al., 2002)Reduced-form model of the vegetation dynamics and of the terrestrial carbon cycle (same resolution as ECBilt).

LOCH (Mouchet and François, 1996)Comprehensive oceanic carbon cycle model (same resolution as CLIO).

AGISM (Huybrechts, 2002)Thermomechanical model of the ice sheet flow + visco-elastic bedrock model + model of the mass balance at the ice-atmosphere and ice-ocean interfaces (10 km x 10 km, L31).

Testing different model configurations

Description of the experiments. Model parameters are selected to provide different model behaviour, e.g. climate

sensitivity, response of the maximum of the MOC to a 0.2 Sv freshwater flux in the North Atlantic, …

Climate sensitivity (K)

Dec

reas

e of

the

max

imum

of

the

MO

C (

%)

1 2 3 4 5

20

40

60

80

100

X E1

X E2

X E3 X E5X E4

X

X

XX

XX

Annual mean temperature anomaly averaged over the northern Hemisphere during the last 1000 years

E2E3

E4

E5

E1

Time

Tem

pera

ture

ano

mal

yTesting different model configurations

Annual mean temperature anomaly averaged over the northern Hemisphere during the last 8000 years

E2E3

E4

E5

E1

Time

Tem

pera

ture

ano

mal

yTesting different model configurations

Model-data comparison of underground temperatures

Borehole reconstructions Concept

Geothermalgradient

Summer Winter

Model-data comparison of underground temperatures

Borehole reconstructionsConcept

Model-data comparison of underground temperatures

Gonzalez-Rouco et al. 2006

ForwardForward modelmodel

894 grid points894 grid points

Inversion + Lat weighted avg.Inversion + Lat weighted avg.

Replicating the borehole method using ECHO-G GCM as surrogate reality

Model SATReconstruction

Model-data comparison of underground temperatures

Stevens et al. 2007

Forward-modeled profiles produced from a simulation performed using ECHO-G compared to observations (in black). The various grey, red and green cruves are computed from model results suing various reference level.

We need an adequate reference to compute anomalies !

E2E3

E4

E5

E1

Changes in sea-ice extent in the Arctic

Location of the September ice edge in the 5 experiments

Pre-industrial conditions 1980-2000 averages

Goosse et al. 2007

E2E3

E4

E5

E1

Changes in sea-ice extent in the Arctic

Location of the September ice edge in the 5 experiments

Early Holocene conditions(8kyr Bp)

2040-2060 averages (Scenario Sres B1)

Goosse et al. 2007

Goosse et al. 2007

Link between the minimum Arctic sea ice extent (in 106 km2) for the early Holocene and the period 2040-2060 AD (scenario SRES B1)

Changes in sea-ice extent in the Arctic

Changes in sea-ice extent in the Arctic

Time evolution of the minimum ice extent in the Arctic over the period 1900-2100 AD

Scenario SRES B1 Scenario SRES A2

Goosse et al. 2007

Conclusions

Paleo-proxy data could efficiently be used to constrain model behavior.

They could provide complementary information compared to the one obtained from the recent past.

Accurate data are required, with a good spatial sampling and one should take care of the methodology used for model-data comparison.