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The influence of external forcing on subdecadal variability of regional surface temperature in CMIP5 simulations of the last millennium
Author(s) -
Le Thanh,
Sjolte Jesper,
Muscheler Raimund
Publication year - 2016
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2015jd024423
Subject(s) - climatology , forcing (mathematics) , radiative forcing , climate model , atmospheric sciences , coupled model intercomparison project , environmental science , arctic oscillation , greenhouse gas , climate change , surface air temperature , physics , geology , oceanography , northern hemisphere
We use Granger causality to investigate the influences of external forcings on subdecadal variability of regional near‐surface air temperature (SAT) in past millennium simulations (period 850–1850 A.D.) of the Coupled Model Intercomparison Project Phase 5 (CMIP5) models. Our results strengthen the conclusion for robust influence of volcanic forcing on SAT during preindustrial times of the last millennium. The SAT response to solar variations is detected in tropical and subtropical regions. In other regions, this response is weak. The impact of greenhouse gases (GHGs) radiative forcing to regional SAT is weak and uncertain. This is most probably due to the low amplitude of the variations in GHGs and hence weak GHGs forcing during the preindustrial millennium. The low agreement between models in simulating the impacts of solar variations on SAT in several regions suggests the different dynamical responses in these models, possibly associated with inaccurate parameterization of the processes related to solar forcing. Our analysis suggests that internal climate variability played a more significant role than external forcings in short‐term SAT variability in the regions of the North Atlantic, the North Pacific, the Arctic, the Antarctic Peninsula, and its surrounding oceans. The possibility of long‐term impacts of external forcings on SAT and the uncertainties that might be contained due to effects of internal climate modes other than El Niño–Southern Oscillation underscore the necessity for a more detailed understanding of the dynamical response of SAT to external forcings.