北米の気候に人間による影響の検出

David J Karoly¹, Karl Braganza, Peter A Stott

¹School of Meteorology, University of Oklahoma, Norman, OK 73019, USA. dkaroly@ou.edu

Science (New York, N.Y.)

|November 15, 2003

まとめ

20世紀における北米の気候変動は,地表温度変動を用いて調査された. 1950年から1999年にかけての温暖化は,人間による温室効果ガスの増加と一致し,自然的ではなかった.

科学分野:

気候学気候学
環境科学環境科学
大気科学大気科学

背景:

大規模な地表温度変動の調査は,気候変動を理解するために不可欠です.
北米の20世紀の気候パターンは,気候変動研究のための重要な地域を提供します.

研究の目的:

表面温度変動指標を用いて,北米における20世紀の気候変動を分析する.
観測された気温動向の要因を特定し,自然変動と人為的影響を区別する.

主な方法:

大規模な表面温度変動のいくつかの指標を利用した.
観測されたインデックス変動をシミュレートするために複数の気候モデルを使用した.
観測されたデータの傾向を気候モデルシミュレーションと比較した.

主要な成果:

気候モデルは,観測された温度指標の変動性をうまくシミュレートしました.
1950年から1999年の北米の気温の変化は,自然的な気候の変動のみによる可能性は低い.
1900年から1949年までの観測された温暖化は,主に自然気候の変動によって引き起こされた可能性が高い.

結論:

1950-1999年に観測された北米の温暖化傾向は,人類による強制 (温室効果ガス,硫酸エアロゾール) を含むシミュレーションと一致しています.
この発見は,人間の活動が20世紀後半に北米の気候に大きな影響を与えたことを示唆している.
自然な気候の変動が,20世紀前半に観測された温暖化のほとんどを説明している可能性が高い.

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