報告書番号

U97034

タイトル（和文）

大気・海洋結合モデル（ＮＣＡＲ・ＣＳＭ）による全球温暖化予測

タイトル（英文）

GLOBAL WARMING PROJECTION FOR 125 YEARS USING NCAR CSM COUPLED MODEL

概要 （図表や脚注は「報告書全文」に掲載しております）

ＮＣＡＲ共同研究の一環として，最新の大気・海洋結合モデルにより温暖化予測を実施した。ＣＯ２濃度は，ＩＰＣＣシナリオ９２ａ（年率０．７％）にごく近い年率１％で増加させ，約３倍強のＣＯ２濃度に達する１１５年間の漸増計算を行った。主な結果は次の通りである。１）全球地表面温度は２×ＣＯ２時に約１．５度，３×ＣＯ２時に約２．３度上昇し，高緯度地域ほど昇温が顕著である。フラックス調整なしの温暖化予測は世界初の成果である。２）全球年間降水量は，２×ＣＯ２時で約２５ｍｍ，３×ＣＯ２時で約４３ｍｍ増加する。３）海流の流量は，メキシコ湾流の減少を除き，変化は少ない。しかし，中深層の流れは全球的に弱くなる傾向にある。４）南北両半球の海氷が減少し，３×ＣＯ２時では体積は現状の約５０％にまで減少する。高緯度地域の著しく不均一な気温上昇は，海氷が融解するためと推察される。今後，この結果をもとに台風や東アジアの温暖化を高分解能で予測する。

概要 （英文）

RECENTLY, NCAR (NATIONAL CENTER FOR ATMOSPHERIC RESEARCH) HAS DEVELOPED CSM, A NEW COUPLED CLIMATE MODEL. THIS IS THE FIRST CLIMATE MODEL THAT CAN SIMULATE THE PRESENT CLIMATE WITHOUT FLUX CORRECTION. THROUGH COLLABORATION BETWEEN CRIEPI AND NCAR, A SIMULATION FOR THE 125-YEAR CSM RUN WAS PERFORMED IN JAPAN. IN THIS SIMULATION, CO2 LEVELS WERE SET TO INCREASE AT 1% YEAR CONSIDERING THE IPCC EMISSION SCENARIO 92A (0.7%/YEAR). AT THIS RATE, THE CO2 CONCENTRATION IS DOUBLE THE PRESENT LEVEL AFTER 70 YEARS AND IS TRIPLE THE PRESENT LEVEL AFTER ABOUT 110 YEARS. THE SIMULATION WAS PERFORMED ON A 32-PROCESSOR SX-4 SUPERCOMPUTER AT THE NEC FACTORY IN FUCHU, WITH ASSISTANCE FROM THE NEC US SUBSIDIARY, HNSX SUPERCOMPUTERS. EACH YEAR OF MODEL TIME TOOK ABOUT 90 MINUTES TO RUN ON THE SX-4. A NEW SONY HIGH-DENSITY TAPE DRIVE (DTF) WAS USED TO RECORD THE ENTIRE DATA SET OF ABOUT 170 GB. THE PRELIMINARY RESULTS OF THE 125-YEAR SIMULATION ARE AS FOLLOWS: (1)THE GLOBAL MEAN SURFACE TEMPERATURE INCREASES BY 1.5DEGREE AT 2 CO2 AND BY 2.3DEGREE AT 3 CO2. WARMING DOES NOT TAKE PLACE UNIFORMLY AND IS MORE INTENSE AT HIGHER LATITUDES THAN AT LOWER LATITUDES. FOR EXAMPLE, THE SURFACE TEMPERATURE NEAR THE KAMCHATKA PENINSULA INCREASES BY ABOUT 4DEGREE AT 2CO2. (2)THE GLOBAL MEAN PRECIPITATION INCREASES BY 2.3% AT 2 CO2 AND BY 3.8% AT 3 CO2. A RELATIVELY HIGH INCREASE IN PRECIPITATION OCCURS IN THE ASIA MONSOON REGION.(3)THERE IS LITTLE CHANGE IN OCEAN CURRENT VOLUMES, EXCEPT FOR A DECREASE IN THE GULF STREAM. BUT MID- AND DEEP-OCEAN CURRENTS BECOME WEAKER. (4)SEA ICE IN BOTH THE NORTHERN AND SOUTHERN HEMISPHERS DECREASES TO 80% AND 50% OF THE PRESENT VOLUME AT 2 CO2 AND 3 CO2, RESPECTIVELY. THE NON-UNIFORMITY OF WARMING MAY BE CAUSED BY MELTING OF SEA ICE. CRIEPI WILL ANALYZE THESE DATA IN MORE DETAIL AND USE THEM WITH A REGIONAL CLIMATE MODEL TO STUDY THE CLIMATOLOGY OF TROPICAL CYCLONES AND SYNOPTIC-SCALE DISTURBANCES OVER EAST ASIA.

報告者

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