The effect of obliquity-driven changes on paleoclimate sensitivity during the late Pleistocene

• Main Authors: Köhler, Peter, Knorr, Gregor, Stap, Lennert, Ganopolski, Andrey, de Boer, Bas, van de Wal, Roderik S. W., Barker, Stephen, Rüpke, Lars H.
• Format: Conference Object
• Language: unknown
• Published: 2018
• Subjects: Ice Sheet
• Online Access: https://epic.awi.de/id/eprint/46969/; https://hdl.handle.net/10013/epic.7ab99ac7-3dc9-4c83-8309-fd06448557ff

Some studies suggest that specific equilibrium climate sensitivity S might be state-dependent. Reanalyzing existing paleodata of global mean surface temperature ∆Tg and radiative forcing ∆R of CO2 and land ice albedo for the last 800,000 years we show that this state-dependency of S is only found if ∆Tg is based on reconstructions, and not when ∆Tg is based on model simulations. Furthermore, during times of decreasing obliquity (periods of land-ice sheet growth and sea level fall) the multi-millennial component of reconstructed ∆Tg is diverging from atmospheric CO2, while in simulations both variables vary more synchronously. For a reconstruction-based extrapolation of S to the future we eliminate these periods due to an expected sea level rise. Consequently, S determined from proxy-based reconstructions without these data with strong ∆Tg-CO2 divergence is less state-dependent or even constant (state-independent), and yields into an equilibrium warming for 2 × CO2 of 1.9–3.8 K.