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Spread of model climate sensitivity linked to double‐Intertropical Convergence Zone bias
Author(s) -
Tian Baijun
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl064119
Subject(s) - intertropical convergence zone , climatology , convergence (economics) , constraint (computer aided design) , climate model , environmental science , metric (unit) , sensitivity (control systems) , atmospheric sciences , meteorology , climate change , geography , mathematics , geology , precipitation , oceanography , economics , electronic engineering , engineering , economic growth , operations management , geometry
Despite decades of climate research and model development, two outstanding problems still plague the latest global climate models (GCMs): the double‐Intertropical Convergence Zone (ITCZ) bias and the 2−5°C spread of equilibrium climate sensitivity (ECS). Here we show that the double‐ITCZ bias and ECS in 44 GCMs from Coupled Model Intercomparison Project Phases 3/5 are negatively correlated. The models with weak (strong) double‐ITCZ biases have high (low)‐ECS values of ~4.1(2.2)°C. This indicates that the double‐ITCZ bias is a new emergent constraint for ECS based on which ECS might be in the higher end of its range (~4.0°C) and most models might have underestimated ECS. In addition, we argue that the double‐ITCZ bias can physically affect both cloud and water vapor feedbacks (thus ECS) and is a more easily measured emergent constraint for ECS than previous ones. It can be used as a performance metric for evaluating and comparing different GCMs.