A state-dependent quantification of climate sensitivity based in paleo data of the last 2.1 million years

Peter Köhler*, L.B. Stap, A.S. von der Heydt, B. de Boer, R.S.W. van de Wal, Jonah Bloch-Johnson

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The evidence from both data and models indicates that specific equilibrium climate sensitivity S[X] — the global annual mean surface temperature change (DTg) as a response to a change in radiative forcing X (DR[X]) — is state-dependent. Such a state dependency implies that the best fit in the scatter plot of (DTg versus DR[X] is not a linear regression, but can be some non-linear or even non-smooth function. While for the conventional linear case the slope (gradient) of the regression is correctly interpreted as the specific equilibrium climate sensitivity S[X], the interpretation is not straightforward in the non-linear case. We here explain how such a state-dependent scatter plot needs to be interpreted, and provide a theoretical understanding — or generalization — how to quantify S[X] in the non-linear case. Finally, from data covering the last 2.1 Myr we show that — due to state dependency — the specific equilibrium climate sensitivity which considers radiative forcing of CO2 and land ice sheet (LI) albedo, S[CO2;LI], is larger during interglacial states than during glacial conditions by more than a factor two.
Original languageEnglish
Pages (from-to)1102-114
Number of pages13
JournalPaleoceanography
Volume32
Issue number11
Early online date4 Oct 2017
DOIs
Publication statusPublished - Nov 2017

Keywords

  • climate sensitivity
  • Pleistocene

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