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Development of a system emulating the global carbon cycle in Earth system models
1Japan Agency for Marine-Earth Science and Technology 3173-25 Showamachi, Kanazawa-ku, Yokohama, 236-0001, Japan
2Center for Climate System Research, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-8568, Japan
Abstract. By combining the strong points of general circulation models (GCMs), which contain detailed and complex processes, and Earth system models of intermediate complexity (EMICs), which are quick and capable of large ensembles, we have developed a loosely coupled model (LCM) which can represent the outputs of a GCM-based Earth system model using much smaller computational resources.
We address the problem of relatively poor representation of precipitation within our EMIC, which prevents us from directly coupling it to a vegetation model, by coupling it to a precomputed transient simulation using a full GCM. The LCM consists of three components: an EMIC (MIROC-lite) which consists of a 2-D energy balance atmosphere coupled to a low resolution 3-D GCM ocean including an ocean carbon cycle; a state of the art vegetation model (Sim-CYCLE); and a database of daily temperature, precipitation, and other necessary climatic fields to drive Sim-CYCLE from a precomputed transient simulation from a state of the art AOGCM. The transient warming of the climate system is calculated from MIROC-lite, with the global temperature anomaly used to select the most appropriate annual climatic field from the pre-computed AOGCM simulation which, in this case, is a 1% pa increasing CO2 concentration scenario.
By adjusting the climate sensitivity of MIROC-lite, the transient warming of the LCM could be adjusted to closely follow the low sensitivity (4.0 K) version of MIROC3.2. By tuning of the physical and biogeochemical parameters it was possible to reasonably reproduce the bulk physical and biogeochemical properties of previously published CO2 stabilisation scenarios for that model. As an example of an application of the LCM, the behavior of the high sensitivity version of MIROC3.2 (with 6.3 K climate sensitivity) is also demonstrated. Given the highly tunable nature of the model, we believe that the LCM should be a very useful tool for studying uncertainty in global climate change.
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Citation: Tachiiri, K., Hargreaves, J. C., Annan, J. D., Oka, A., Abe-Ouchi, A., and Kawamiya, M.: Development of a system emulating the global carbon cycle in Earth system models, Geosci. Model Dev. Discuss., 3, 61-97, 2010. Bibtex EndNote Reference Manager
