Open AccessCloud feedbacks on greenhouse warming in the superparameterized climate model SP‐CCSM 4
Author(s) -
Bretherton Christopher S.,
Blossey Peter N.,
Stan Cristiana
Publication year - 2014
Publication title -
journal of advances in modeling earth systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.03
H-Index - 58
ISSN - 1942-2466
DOI - 10.1002/2014ms000355
Subject(s) - environmental science , cloud feedback , global warming , atmospheric sciences , climatology , cloud albedo , climate model , greenhouse gas , shortwave , cloud forcing , climate sensitivity , cloud computing , cloud cover , climate change , geology , radiative transfer , oceanography , physics , quantum mechanics , computer science , operating system
Cloud feedbacks on greenhouse warming are studied in a superparameterized version of the Community Climate System Model (SP‐CCSM4) in an atmospheric component SP‐CAM4 that explicitly simulates cumulus convection. A 150 year simulation in an abrupt quadrupling of CO 2 is branched from a control run. It develops moderate positive global cloud feedback and an implied climate sensitivity of 2.8 K comparable to the conventionally parameterized CCSM4 and the median of other modern climate models. All of SP‐CCSM4's positive shortwave cloud feedback is due to a striking decrease in low cloud over land, which is much more pronounced than in most other climate models, including CCSM4. Four other cloud responses – decreased midlevel cloud, more Arctic water and ice cloud, a slight poleward shift of midlatitude storm track cloud, and an upward shift of high clouds – are also typical of conventional global climate models. SP‐CCSM4 does not simulate the large warming‐induced decrease in Southern Ocean cloud found in CCSM4. Two companion uncoupled SP‐CAM4 simulations, one with a uniform 4 K sea‐surface temperature increase and one with quadrupled CO 2 but fixed SST, suggest that SP‐CCSM4's global‐scale cloud changes are primarily mediated by the warming, rather than by rapid adjustments to increased CO 2 . SP‐CAM4 show spatial patterns of cloud response qualitatively similar to the previous‐generation superparameterized SP‐CAM3, but with systematically more positive low cloud feedbacks over low‐latitude land and ocean.