Prediction of Dryness in the Semi-Arid regions By the Greenhouse Warming Model

March 14,2000

Recent research results of the FRSGC will be presented at Kokuyo Hall (1-8-35 Konan, Minato-ku, Tokyo) on March 24-25, 2000, during the Annual Symposium, under the title "The Forefront of Research on Global Change". Research highlights are introduced here as follows:

1. Dr. Shukuro Manabe, Director of the Global Warming Research Program of the FRSGC, which is jointly promoted by NASDA (President, Mr. Shun-ichiro Yamanouchi) and JAMSTEC (President, Mr. Takuya Hirano), in cooperation with the U.S. Institute of Geophysics and Fluid Dynamics, has for the first time, predicted a large scale decreasing of soil moisture in the world's semi-arid regions, including the basins of the Tigris-Euphrates rivers and in Southern California. They presented their findings in the scientific journal Climatic Change. According to their findings, soil moisture in areas such as the area around the Mediterranean Sea, Central Africa, and the southwestern part of North America, which were once fertile and considered granaries, could decrease by approximately 30% by the latter half of the 21st century (figure 1).

2. The cause of decreasing soil moisture is due to the increase in land surface temperatures associated with global warming, along with saturated vapor pressure increase, thereby enhancing evaporation. In semi-arid regions, the relative humidity of the lower troposphere decreases with global warming, and the precipitation rate hardly increases, thus decreasing soil moisture to a greater extent. This is especially true in many semi-arid regions, which lack water in the first place, where the scarcity of water becomes an even greater possibility. If the situation worsens, there is a strong possibility that this may be lead to a worldwide problem including Japan, which relies on the import of cereals from abroad.

3. Dr. Ayako Abe (research staff of the Center for Climate System Research, the Univ. of Tokyo) of the FRSGC, has duplicated the same results by using a higher resolution global warming model in her calculation, and has clarified local characteristics in more detail. In the future, researchers at the FRSGC aim to predict changes of features such as soil moisture, atmospheric temperatures, and river-runoffs by making super high resolution prediction experiments of global warming utilizing the Earth Simulator.

[Reference materials]

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