Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
doi:10.5194/cp-2016-23
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Technical note
15 Mar 2016
Review status
This discussion paper has been under review for the journal Climate of the Past (CP). The revised manuscript was not accepted.
Technical Note: Calculating state dependent equilibrium climate sensitivity from palaeodata
Peter Köhler1, Lennert B. Stap2, Anna S. von der Heydt2, Bas de Boer3, and Roderik S. W. van de Wal2 1Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung (AWI), P.O. Box 12 01 61, 27515 Bremerhaven, Germany
2Institute for Marine and Atmospheric research Utrecht (IMAU), Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
3School of Earth and Environment, University of Leeds, Leeds, UK
Abstract. The evidence from both data and models indicate that specific equilibrium climate sensitivity S[X] – the global annual mean surface temperature change (∆Tg) as a response to a change in radiative forcing X (∆R[X]) – is state dependent. Such a state dependency implies that the best fit in the scatter plot of ∆Tg versus ∆R[X] is not a linear regression, but for instance a higher order polynomial. 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 elaborate how such a state dependent scatter plot needs to be interpreted, and provide a theoretical understanding how to calculate S[X] in the non-linear case.

Citation: Köhler, P., Stap, L. B., von der Heydt, A. S., de Boer, B., and van de Wal, R. S. W.: Technical Note: Calculating state dependent equilibrium climate sensitivity from palaeodata, Clim. Past Discuss., doi:10.5194/cp-2016-23, in review, 2016.
Peter Köhler et al.
Peter Köhler et al.

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Short summary
Evidence indicate that specific equilibrium climate sensitivity, the global annual mean surface temperature change as a response to a change in radiative forcing, is state dependent. We here show that the interpretation of data in the state-dependent case is not straightforward. We analyse the differences of a point-wise approach and one based on a piece-wise linear analysis, combine both, compare with potential model results and apply the theoretical concepts to data of the last 800 kyr.
Evidence indicate that specific equilibrium climate sensitivity, the global annual mean surface...
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