New THC paper

There is a new paper intercomparing the response of the THC to increasing GHG forcing up to 4xCO2, more evidence for the view (see posts here) that the THC won't collapse.

Gregory, J.M., K.W. Dixon, R.J. Stouffer, A.J. Weaver, E. Driesschaert, M. Eby, T. Fichefet, H. Hasumi, A. Hu, J.H. Jungclaus, I.V. Kamenkovich, A. Levermann, M. Montoya, S. Murakami, S. Nawrath, A. Oka, A.P. Sokolov and R.B. Thorpe (2005), A Model Intercomparison Of Changes In The Atlantic Thermohaline Circulation In Response To Increasing Atmospheric Co2 Concentration, Geophys . Res . Lett . 32 ( 12 ): Art . No . L12703 Jun 23 2005

As part of the Coupled Model Intercomparison Project, integrations with a common design have been undertaken with eleven different climate models to compare the response of the Atlantic thermohaline circulation ( THC ) to time-dependent climate change caused by increasing atmospheric CO2 concentration. Over 140 years, during which the CO2 concentration quadruples, the circulation strength declines gradually in all models, by between 10 and 50%. No model shows a rapid or complete collapse, despite the fairly rapid increase and high final concentration of CO2. The models having the strongest overturning in the control climate tend to show the largest THC reductions. In all models, the THC weakening is caused more by changes in surface heat flux than by changes in surface water flux. No model shows a cooling anywhere, because the greenhouse warming is dominant.


Blogger James Annan said...

Glad to see they agree with us :-)

9:33 pm  
Blogger Belette said...

Ah, but you get THC collapses which (hobby horse) seems to a thing of MIC's not GCMs...

10:17 pm  
Blogger James Annan said...

Not so. It's a matter of time scale. We don't get THC collpase in 100 years either! They haven't run their models long enough to se what happens next! Note also that in the paper it says they didn't get different behaviour in EMICS and GCMs.

Does it mean The Day After Tomorrow wasn't completely realistic after all?

jules (using James' account)

10:49 pm  
Anonymous Anonymous said...

Since I dont get GRL, what was the climate sensitivity at 4xCO2

Eli Rabett

1:05 am  
Blogger James Annan said...

They didn't run to equilibrium and did not report the transient global temp changes, but the equilibrium warming would just be double that at 2xCO2, previously reported at about 2-4.4C for the ensemble of models.

7:38 am  

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