The Effect of Obliquity-Driven Changes on Paleoclimate Sensitivity During the Late Pleistocene

• Published in: Geophysical Research Letters
• Main Authors: Köhler, Peter, Knorr, Gregor, Stap, Lennert B., Ganopolski, Andrey, de Boer, Bas, van de Wal, Roderik S.W., Barker, Stephen, Rüpke, Lars H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2018
• Subjects: climate sensitivity; ECS; Pleistocene; proxies; simulation; state dependence; /dk/atira/pure/sustainabledevelopmentgoals/climate_action; name=SDG 13 - Climate Action; /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; name=SDG 14 - Life Below Water; Ice Sheet
• Online Access: https://research.vu.nl/en/publications/c447ee5e-2d15-4e4f-9cbd-d6f5e376c185; https://doi.org/10.1029/2018GL077717; https://hdl.handle.net/1871.1/c447ee5e-2d15-4e4f-9cbd-d6f5e376c185; http://www.scopus.com/inward/record.url?scp=85050552064&partnerID=8YFLogxK; http://www.scopus.com/inward/citedby.url?scp=85050552064&partnerID=8YFLogxK

We reanalyze existing paleodata of global mean surface temperature ΔT g and radiative forcing ΔR of CO 2 and land ice albedo for the last 800,000 years to show that a state-dependency in paleoclimate sensitivity S, as previously suggested, is only found if ΔT g is based on reconstructions, and not when ΔT g is based on model simulations. Furthermore, during times of decreasing obliquity (periods of land ice sheet growth and sea level fall) the multimillennial component of reconstructed ΔT g diverges from CO 2 , while in simulations both variables vary more synchronously, suggesting that the differences during these times are due to relatively low rates of simulated land ice growth and associated cooling. To produce a reconstruction-based extrapolation of S for the future, we exclude intervals with strong ΔT g -CO 2 divergence and find that S is less state-dependent, or even constant state-independent), yielding a mean equilibrium warming of 2–4 K for a doubling of CO 2 .