The Roles of CO₂ and Orbital Forcing in Driving Southern Hemispheric Temperature Variations during the Last 21 000 Yr

• Published in: Journal of climate Vol. 22; no. 7; pp. 1626 - 1640
• Main Authors: Timmermann, Axel, Timm, Oliver, Stott, Lowell, Menviel, Laurie
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.04.2009
• Subjects: Albedo; Antarctic regions; Atmospherics; Carbon dioxide; Carbon dioxide concentration; Climate change; Climate models; Earth sciences; Earth, ocean, space; Exact sciences and technology; Gases; Greenhouse effect; Greenhouse gases; Heat; Hydrology; Ice; Ice cores; Ice sheets; Insolation; Isotopes; Marine and continental quaternary; Meteorology; Ozone; Paleoclimatology; Sea ice; Seasonal variations; Seasons; Simulation; Simulations; Southern Hemisphere; Summer; Surficial geology; Temperature; Temperature variations; Terminations; Southern Hemisphere; Antarctica; Southern Ocean; Insolation; Carbon dioxide; Atmosphere cryosphere interaction; digital simulation; upper Quaternary; greenhouse gas; feedback; Wurm; sea ice; Forcing; Cenozoic; Triggering; albedo; climate change; Southern Hemisphere; climate variations; Quaternary; climate warming; Orbital element; Climate models; deglaciation; Dynamical climatology; upper Pleistocene; Phanerozoic; Holocene; Pleistocene
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/2008jcli2161.1

Transient climate model simulations covering the last 21 000 yr reveal that orbitally driven insolation changes in the Southern Hemisphere, combined with a rise in atmospheric pCO₂, were sufficient to jumpstart the deglacial warming around Antarctica without direct Northern Hemispheric triggers. Analyses of sensitivity experiments forced with only one external forcing component (greenhouse gases, ice-sheet forcing, or orbital forcing) demonstrate that austral spring insolation changes triggered an early retreat of Southern Ocean sea ice starting around 19–18 ka BP. The associated sea ice–albedo feedback and the subsequent increase of atmospheric CO₂ concentrations helped to further accelerate the deglacial warming in the Southern Hemisphere. Implications for the interpretation of Southern Hemispheric paleoproxy records are discussed.