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How may low‐cloud radiative properties simulated in the current climate influence low‐cloud feedbacks under global warming?
Author(s) -
Brient F.,
Bony S.
Publication year - 2012
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 - 10.1029/2012gl053265
Subject(s) - cloud feedback , cloud cover , climate model , environmental science , climatology , cloud forcing , radiative transfer , atmospheric sciences , cloud computing , global warming , climate change , cloud fraction , greenhouse gas , climate sensitivity , physics , geology , oceanography , quantum mechanics , computer science , operating system
The influence of cloud modelling uncertainties on the projection of the tropical low‐cloud response to global warming is explored by perturbing model parameters of the IPSL‐CM5A climate model in a range of configurations (realistic general circulation model, aqua‐planet, single‐column model). While the positive sign and the mechanism of the low‐cloud response to climate warming predicted by the model are robust, the amplitude of the response can vary considerably depending on the model tuning parameters. Moreover, the strength of the low‐cloud response to climate change exhibits a strong correlation with the strength of the low‐cloud radiative effects simulated in the current climate. We show that this correlation primarily results from a local positive feedback (referred to as the “beta feedback”) between boundary‐layer cloud radiative cooling, relative humidity and low‐cloud cover. Based on this correlation and observational constraints, it is suggested that the strength of the tropical low‐cloud feedback predicted by the IPSL‐CM5A model in climate projections might be overestimated by about fifty percent.