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. Portmann1,2,41Biodiversity 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
Received: 11 Nov 2014 – Accepted for review: 15 Nov 2014 – Discussion started: 15 Dec 2014
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.
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, doi:10.5194/cpd-10-4535-2014, 2014.