Open AccessRole of the mean state for the Southern Hemispheric jet stream response to CO2 forcing in CMIP6 models
Author(s) -
Paul Edwin Curtis,
Paulo Ceppi,
Giuseppe Zappa
Publication year - 2020
Publication title -
environmental research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.37
H-Index - 124
ISSN - 1748-9326
DOI - 10.1088/1748-9326/ab8331
Subject(s) - jet stream , coupled model intercomparison project , forcing (mathematics) , climatology , jet (fluid) , environmental science , climate model , latitude , atmospheric sciences , climate change , geology , physics , geodesy , mechanics , oceanography
Global climate models indicate that the Southern Hemispheric (SH) jet stream shifts poleward in response to CO 2 forcing, but the magnitude of this shift remains highly uncertain. Here we analyse the SH jet stream response to 4×CO 2 forcing in Coupled Model Intercomparison Project phase 6 (CMIP6) simulations, and find a substantially muted jet shift during winter compared with CMIP5. We suggest this muted response results from a more poleward mean jet position, consistent with a strongly reduced bias in jet position relative to the reanalysis during 1980–2004. The improved mean jet position cannot be explained by changes in the simulated sea surface temperatures. Instead, we find indications that increased horizontal grid resolution in CMIP6 relative to CMIP5 has contributed to the higher mean jet latitude, and thus to the reduced jet shift under CO 2 forcing. These results imply that CMIP6 models can provide more realistic projections of SH climate change.