Elucidation of climate feedback codependency towards fundamental theory of global warming

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K03968
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17020:Atmospheric and hydrospheric sciences-related
• Research Institution: The University of Tokyo
• Principal Investigator: Yoshimori Masakazu 東京大学, 大気海洋研究所, 准教授 (20466874)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 地球温暖化 / 気候フィードバック / 気候モデル / 上層雲

Outline of Final Research Achievements

Many previous studies quantified the radiative effect of changes in atmospheric constituents such as water vapor and clouds separately, but the codependency of feedbacks has not been explored sufficiently. In this study, the relation among feedback processes was investigated and the validity of a new framework of climate feedbacks based on a basic theoretical argument was demonstrated using an atmospheric general circulation model. This study also proposed re-interpretation of relatively well accepted FAT theory in which tropical anvil cloud temperature is invariant before and after the global warming, as well as PHAT theory, a modified version of the FAT theory in which slight warming of anvil cloud temperature is suggested. Furthermore, discussion was made on the “predictability” of the cloud feedback under the global warming from the current climate information alone.

Free Research Field

気候変動

Academic Significance and Societal Importance of the Research Achievements

二酸化炭素濃度の上昇に対する気温上昇量を知ることは、気温上昇の上限目標に対して人類が排出する二酸化炭素の許容量を判断し、政策を検討する上で不可欠な情報である。世界の平均気温の上昇量は気候フィードバックと呼ばれる、気温上昇に伴って生じる水蒸気や雲の変化が引き起こす更なる地球の放射収支の不釣り合いの影響を強く受ける。本研究は、これまで進展が遅く未確立であるフィードバック基礎理論の体系化に貢献するものである。注目するフィードバックが温暖化を増幅する働きがあるのか、抑制する働きがあるのか、中立なものなのか、フィードバック間の連動性を調べることによって議論し、いくつかの新しい概念的な発展を実現させた。