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Title

Comments on "Reconstructing the NH mean temperature: Can underestimation of trends and variability be avoided?"

Abstract

In a recent paper, Bo Christiansen presents and discusses 'LOC,' a methodology for reconstructing past climate that is based on local regressions between climate proxy time series and instrumental time series (Christiansen 2010, hereafter C2010). LOC respects two important scientific facts about proxy data which are often overlooked: 1) many proxies are likely influenced by strictly local temperature, and 2) to reflect causality, the proxies must be written as functions of climate, not vice versa. There are, however, several shortcomings to the LOC method: uncertainty is not propagated through the multiple stages of the analysis, the effects of observational errors in the instrumental observations are not considered, and as the proxies become uninformative of climate, the variance of a reconstruction produced by LOC becomes unbounded - a result which is clearly unphysical. This comment interprets the LOC method in the context of recently proposed Bayesian Hierarchical reconstruction methods, and describes how LOC can be derived as a frequentist implementation of a special case of two previously published methods: that described in Li et al. (2010) and the BARCAST approach of Tingley and Huybers (2010a). Recasting LOC within a Bayesian hierarchical framework allows for an inference scheme that propagates uncertainty through the multiple stages of the model. In addition, prior information about the target temperature process can be included in the hierarchical model, and doing so insures that the variance of the reconstruction remains bounded in the limit as the proxies become uninformative of the target process.

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document

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http://n2t.net/ark:/85065/d7sf2wp7

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eng

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geoscientificInformation

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publication

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2016-01-01T00:00:00Z

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publication

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2012-05-01T00:00:00Z

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Copyright 2012 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

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OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

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