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

Peter Köhler*, Gregor Knorr, Lennert B. Stap, Andrey Ganopolski, Bas de Boer, Roderik S.W. van de Wal, Stephen Barker, Lars H. Rüpke

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

We reanalyze existing paleodata of global mean surface temperature ΔTg and radiative forcing ΔR of CO2 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 ΔTg is based on reconstructions, and not when ΔTg 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 ΔTg diverges from CO2, 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 ΔTg-CO2 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 CO2.

Original languageEnglish
Pages (from-to)6661-6671
Number of pages11
JournalGeophysical Research Letters
Volume45
Issue number13
DOIs
Publication statusPublished - 16 Jul 2018

Funding

This is work institutional-funded at AWI via the research program PACES-II of the Helmholtz Association. It contributes to PALMOD, the German Paleomodeling Research Project funded by BMBF. Gregor Knorr acknowledges funding by Helmholtz Climate Initiative REKLIM (Regional Climate Change), a joint research project of the Helmholtz Association of German research centers (HGF). B. de Boer is funded by NWO Earth and Life Sciences (ALW), project 863.15.019. This work contributes to the Netherlands Earth System Science Centre (NESSC). We thank Tobias Friedrich for providing data and Emma Smith for language editing. No new data have been generated for this work. All analyzed data sets have been taken from the cited literature.

FundersFunder number
Helmholtz Climate Initiative REKLIM
Helmholtz-Gemeinschaft
Bundesministerium für Bildung und Forschung
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research
Nederlandse Organisatie voor Wetenschappelijk Onderzoek863.15.019
Helmholtz Association

    Keywords

    • climate sensitivity
    • ECS
    • Pleistocene
    • proxies
    • simulation
    • state dependence

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