The Azimuth Project
Earth model of intermediate complexity

Idea

An Earth model of intermediate complexity (or EMIC) resembles a general circulation model or GMC, but calculations are made on longer time-scales and larger spatial scales, allowing for the study of the climate over longer periods: for example, as long as thousands of years. An EMIC typically has a 3d atmosphere and a slab ocean, or a 3d ocean and an energy-moisture balance atmosphere. EMICs have a greater degree of parametrization than GCMs, and this may cause a greater degree of uncertainty in their predictions. For an introduction to EMICs, see:

The authors write:

To bridge the gap between conceptual, inductive, simple and comprehensive, quasi-deductive models, Earth system Models of Intermediate Complexity (EMICs) have been proposed. EMICs are designed to describe the natural Earth system excluding the interaction of humans and nature; humans appear as some external driving force. Hence a more appropriate acronym would be NEMICs instead of EMICs. However, the latter acronym has now become widespread.

EMICs can be characterize in the following way. EMICs include most of the processes described in comprehensive models, albeit in a more reduced, i.e., a more parameterized form. They explicitly simulate the interactions among several components of the natural Earth system, including biogeochemical cycles. On the other hand, EMICs are simple enough to allow for long-term climate simulations over several 10,000 years or even glacial cycles. Similar to comprehensive models, but in contrast to conceptual models, the degrees of freedom of an EMIC exceed the number of adjustable parameters by several orders of magnitude. EMICs are more quasi-deductive models, not inductive deterministic models, although some of the components of an EMIC could belong the this class.

Tentatively, we may define an EMIC in terms of a three-dimensional vector (Claussen, 2000): integration, i.e., the number of components of the natural Earth system being explicitly described in the model including the interaction between them (hence the term integration is used here in the sense of integrated modelling rather than in its original mathematical meaning), number of processes explicitly described, and detail of description.

Examples

We list three examples taken from this paper, which also lists more:

  • Michel Crucifix, Modeling the climate of the Holocene, in Natural Climate Variability and Global Warming: a Holocene Perspective, eds. Richard W. Battarbee and Heather A. Binney, Wiley-Blackwell, Chichester, 2008.

Crucifix writes:

There is presently no comprehensive model or even an EMIC capable of representing the interactions between the slow components of the climate system satisfactorily enough to predic the evolution of ice volume and greenhouse gas concentrations over several glacial-interglacial cycles. There are a few EMICs, however, that are able to simulate the evolution of the atmosphere–ocean–ice-sheet system on those time-scales…

He mentions LLN-2D, CLIMBER-2 and the Toronto climate-ice-sheet model.

LLN-2D

LLN-2D was used to study the last glacial cycle and attempt to predict the next glacial inception:

  • Gallée H., van Ypersele J.P., Fichefet T., Tricot C. and Berger A., Simulation of the last glacial cycle by a coupled, sectorially averaged climate–ice sheet model. Part I: The climate model, Journal of Geophysical Research 96 (1991), 13139–13161.

  • Gallée H., van Ypersele J. P., Fichefet T., Marsiat I., Tricot C. and Berger A., Simulation of the last glacial cycle by a coupled, sectorially averaged climate–ice sheet model. Part II: response to insolation and CO2 variation, Journal of Geophysical Research 97 (1992), 15713–15740.

  • Loutre M. F., Berger A., Crucifix M., Desprat S. and Sánchez-Goñi M.F., Interglacials as simulated by the LLN-2D NH and MoBidiC climate models, in The Climate of Past Interglacials, eds. F. Sirocko, M. Claussen, M.F. Sánchez Goñi and T. Litt, Elsevier, Amsterdam, 2007, pp. 547–582.

CLIMBER-2

  • Petoukhov V., Ganopolski A., Brovkin V., et al., CLIMBER-2: a climate system model of intermediate complexity. Part I: model description and performance for present climate, Climate Dynamics 16 (2000), 1–17.

  • Calov R., Ganopolski A., Claussen M., Petoukhov V. and Greve R, Transient simulation of the last glacial inception. Part I: glacial inception as a bifurcation in the climate system, Climate Dynamics 24 545–561.

  • A. Ganopolski, R. Calov and M. Claussen, Simulation of the last glacial cycle by a coupled, sectorially averaged climate–ice sheet model, Climate of the Past 6 (2010), 229–244.

Abstract: A new version of the Earth system model of intermediate complexity, CLIMBER-2, which includes the three-dimensional polythermal ice-sheet model SICOPOLIS, is used to simulate the last glacial cycle forced by variations of the Earth’s orbital parameters and atmospheric concentration of major greenhouse gases. The climate and icesheet components of the model are coupled bi-directionally through a physically-based surface energy and mass balance interface. The model accounts for the time-dependent effect of aeolian dust on planetary and snow albedo. The model successfully simulates the temporal and spatial dynamics of the major Northern Hemisphere (NH) ice sheets, including rapid glacial inception and strong asymmetry between the ice-sheet growth phase and glacial termination. Spatial extent and elevation of the ice sheets during the last glacial maximum agree reasonably well with palaeoclimate reconstructions. A suite of sensitivity experiments demonstrates that simulated ice-sheet evolution during the last glacial cycle is very sensitive to some parameters of the surface energy and mass-balance interface and dust module. The possibility of a considerable acceleration of the climate ice-sheet model is discussed.

Toronto model

  • Tarasov L. and Peltier W.R., Impact of thermomechanical ice sheet coupling on a model of the 100 kyr ice age cycle, Journal of Geophysical Research 104 (1999), 9517–9545.

category: climate, software