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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/cp-2018-154
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-2018-154
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 21 Nov 2018

Research article | 21 Nov 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).

Empirical estimate of the signal content of Holocene temperature proxy records

Maria Reschke1,2, Kira Rehfeld1,3, and Thomas Laepple1 Maria Reschke et al.
  • 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany
  • 2Institute of Earth and Environmental Sciences, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany
  • 3Institut für Umweltphysik, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany

Abstract. Proxy records from climate archives provide evidence about past climate changes, but the recorded signal is affected by non-climate related effects as well as time uncertainty. As proxy based climate reconstructions are frequently used to test climate models and to quantitatively infer past climate, we need to improve our understanding of the proxy records’ signal content as well as the uncertainties involved. In this study, we empirically estimate signal-to-noise ratios (SNRs) of temperature proxy records used in global compilations of the mid to late Holocene. This is achieved through a comparison of proxy time series from close-by sites of three compilations and model time series data at the proxy sites from two transient Holocene climate model simulations. In all comparisons, we found the mean correlations of the proxy time series on centennial to millennial time scales to be rather low (R<0.2), even for nearby sites, which resulted in low SNR estimates. The estimated SNRs depend on the assumed time uncertainty of the proxy records, the time scale analysed, and the model simulation used. Using the correlation structure of the ECHAM5/MPI-OM simulation, the estimated SNRs on centennial time scales the SNRs ranged from 0.05 – assuming no time uncertainty – to 0.5, for a time uncertainty of 400y. On millennial time scales, the estimated SNRs were generally higher. Use of the TraCE-21ka model simulation correlation structure resulted generally in lower SNR estimates than for ECHAM5/MPI-OM. As the number of available high-resolution proxy records continues to grow, a more detailed analysis of the signal content of specific proxy types should become feasible in the near future. The estimated low signal content of Holocene temperature records should caution against over-interpretation of these kinds of datasets until further studies are able to facilitate a better characterisation of the signal content in paleoclimate records.

Maria Reschke et al.
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We empirically estimate signal-to-noise ratios (SNRs) of temperature proxy records used in global compilations of the mid to late Holocene by comparing the spatial correlation structure of proxy records and climate model simulations accounting for noise and time uncertainty. Our finding of a low signal content of the proxy records or, alternatively, more localised climate variations recorded by proxies than suggested by current model simulations suggest caution when interpreting these datasets.
We empirically estimate signal-to-noise ratios (SNRs) of temperature proxy records used in...
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