Using the Earth Simulator in Global Warming Experiments

Photograph of Dr. Emori
We are happy to introduce our new researcher, Dr. Seita Emori, who has recently joined the Integrated Modeling Research Program of the FRSGC to operate the experimental research using the Earth Simulator.
Dr. Seita Emori (Integrated Modeling Research Program)

From this October, I suspended my work at the National Institute for Environmental Studies in Japan (NIES) for an intended period of three years to participate full-time in the Integrated Modeling Research Program. At NIES, I was mainly involved in developing atmosphere and land-surface models and conducting global warming experiments. My role at the FRSGC is to participate in the global warming experiments using the Earth Simulator.

Global warming experiments refer to experiments that use coupled atmosphere-ocean climate models to calculate how the climate will change in approximately a hundred years from the present, assuming conditions in which the concentration of greenhouse gasses (carbon dioxide, etc.) in the atmosphere are gradually increasing. The results of such types of experiments, which have been conducted to date at various research institutes around the world, are compiled in the Intergovernmental Panel on Climate Change (IPCC) Reports, and this data plays a key role in influencing international negotiations on countermeasures against global warming.

Despite its social importance, however, there do not seem to be many researchers, particularly in Japan,who are willing to undertake such work. The reluctance to engage in this research may well stem from the sense that calculating the climate conditions 100 years hence using the current climate models, which utilize empirical, uncertain formulae, amounts to no more than telling falsehoods, as is often the case.

Nevertheless, I believe that global warming experiments would be significant if they were to be done deliberately. One way would be as Dr. Manabe and his colleagues have been doing, to provide sufficient physical interpretations of the experiment results, and to further the debate on aspects other than the fine details of the empirical formulae. Another way would be to conceive a means that prevents jumping to conclusions from experiment results.

For example, NIES is promoting projects that integrate climate models with ones for social impact and measures against global warming, as shown in the diagram. Within such a framework, the results of the climate model experiments, including knowledge of the uncertainty, are relevantly conveyed to the social impact researchers, without being misconstrued.

Diagram: Concept of integrating climate model research with research on social impacts and countermea-sures against global warming.

In current projects, the models for global warming experiments using the Earth Simulator could be ground breaking in their use of a 0.1 degree grid interval for the ocean, but the atmosphere grid interval is equivalent to 0.56 degree, and it still requires many empirical formulae, so the problem of uncertainty essentially remains unchanged. Nonetheless, the resolution is five to ten times greater than previously possible one, which brings considerable benefits. While simply increasing the resolution does not necessarily improve the model's performance, by investing some time and effort in validation and improvements, the potential exists for models to be created with much fewer systematic errors than before.

Further, these models will allow regional climate features to enter the debate. These features, such as the Baiu front, typhoons, and the heavy snowfall that are experienced on the northern Japan Sea side were insufficiently represented in the earlier crude models. Therefore, this progress is crucial in terms of considering he social impacts of global warming.

To seize on the opportunities pro-vided by the Earth Simulator and conduct meaningful experiments, I strongly feel the need for researchers to cooperate nationwide and proceed with preparations rapidly.

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