Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Technical note
15 Dec 2014
Review status
This discussion paper has been under review for the journal Climate of the Past (CP). A final paper in CP is not foreseen.
Technical Note: Are large error bars desirable? A note on quantitative model-proxy comparison
J. Liakka1,2, J. T. Eronen1,2, H. Tang3, and F. T. Portmann1,2,4 1Biodiversity and Climate Research Centre (LOEWE BiK-F), Frankfurt, Germany
2Senckenberg Gesellschaft für Naturforschung, Frankfurt, Germany
3Department of Geosciences and Geography, University of Helsinki, Helsinki, Finland
4Institute of Physical Geography, Goethe University, Frankfurt, Germany
Abstract. The combined use of proxy records and climate modelling is invaluable for obtaining a better understanding of past climates. However, many methods of model-proxy comparison in the literature are fundamentally problematic because larger errors in the proxy tend to yield a "better" agreement with the model. Here we quantify model-proxy agreement as a function to proxy uncertainty using the overlapping coefficient OVL, which measures the similarity between two probability distributions. We found that the model-proxy agreement is poor (OVL < 50%) if the proxy uncertainty (σp) is greater than three times the model variability (σm), even if the model and proxy have similar mean estimates. Hence only proxies that fulfil the condition σp < 3σm should be used for detailed quantitative evaluation of the model performance.

Citation: Liakka, J., Eronen, J. T., Tang, H., and Portmann, F. T.: Technical Note: Are large error bars desirable? A note on quantitative model-proxy comparison, Clim. Past Discuss., 10, 4535-4552,, 2014.
J. Liakka et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version      Supplement - Supplement
RC C2183: 'Not useful', Anonymous Referee #1, 12 Jan 2015 Printer-friendly Version 
RC C2479: 'needs work', Anonymous Referee #2, 21 Mar 2015 Printer-friendly Version 
J. Liakka et al.


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