Pseudo-proxy tests of the analogue method to reconstruct spatially resolved global temperature during the Common Era

Gómez-Navarro, Juan José; Zorita, Eduardo; Raible, Christoph C.; Neukom, Raphael

doi:https://doi.org/10.5194/cp-13-629-2017

Articles | Volume 13, issue 6

https://doi.org/10.5194/cp-13-629-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/cp-13-629-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 13, issue 6

Research article

|

08 Jun 2017

Research article |

| 08 Jun 2017

Pseudo-proxy tests of the analogue method to reconstruct spatially resolved global temperature during the Common Era

Juan José Gómez-Navarro, Eduardo Zorita, Christoph C. Raible, and Raphael Neukom

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Final revised paper (published on 08 Jun 2017)
Preprint (discussion started on 14 Oct 2016)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

SC1: 'A few comments', James Annan, 31 Oct 2016
- AC1: 'Response to J. D. Annan', Juan José Gómez-Navarro, 13 Jan 2017
RC1: 'Comment by E. Boucher', Etienne Boucher, 30 Nov 2016
- AC2: 'Response to E. Boucher', Juan José Gómez-Navarro, 13 Jan 2017
RC2: 'Review of “Testing the analog method in reconstructing the global mean annual temperature during the common era”', Anonymous Referee #2, 02 Dec 2016
- AC3: 'Response to Reviwer #2', Juan José Gómez-Navarro, 13 Jan 2017
  - AC4: 'Response to handling editor', Juan José Gómez-Navarro, 13 Jan 2017
EC1: 'Editor's conclusions', Joel Guiot, 13 Dec 2016

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Publish subject to minor revisions (review by Editor) (15 Jan 2017) by Joel Guiot

AR by Anna Wenzel on behalf of the Authors (08 Mar 2017) Author's response

ED: Reconsider after major revisions (09 Mar 2017) by Joel Guiot

AR by Juan José Gómez-Navarro on behalf of the Authors (13 Mar 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (13 Mar 2017) by Joel Guiot

RR by Anonymous Referee #2 (10 Apr 2017)

Suggestions for revision or reasons for rejection

Review of “Pseudo-proxy tests of the analogue method to reconstruct spatially resolved global temperature during the Common Era” by Juan José Gómez-Navarro et al.

Generally, I find this paper greatly improved and would recommend that it be published provided that some mainly minor revisions are performed.

In the review that follows, I outline the substantive comments first before listing the minor points.

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It is good that the authors take into account the change in the proxy network back in time and this is now clearer in the text but I feel this point should be expanded on when describing the performance of the reconstruction. The period in which the correlations to the true values etc are evaluated will presumably impact the results due to the difference in coverage through time. In particular, when comparing the correlations in the figure 8 to figures 5,6,7 are they calculated over the same time period? If not wouldn’t the difference in proxy coverage effect the results, making any comparison problematic? Also in the figures, is the proxy network plotted showing maximum availability? If so I think it would be useful to state that some of these proxies do not cover the full period over which the correlations are calculated and perhaps the location of the proxies which do cover the full period could be indicated.

Somewhere in the paper it should be mentioned that the reconstructions show less homogeneity back through time than the models (e.g. co-variability between the NH and SH) see Neukom et al and the paper by the PAGES 2k-PMIP3 group (Continental-scale temperature variability in PMIP3 simulations and PAGES 2k regional temperature reconstructions over the past millennium). This could mean that the performance of the PPE examples, particularly in the SH, shown here may be optimistic when compared to the performance in a real world scenario.

Figure 4 – As mentioned in my previous review I really think this figure would illustrate the point you wish to make far better if you make panels b and d a perfect square and put a x=y line through it. This would make it much more intuitive and clearer to interpret. In addition I think marking where the major volcanic eruptions occurred would help. At the moment I am struggling to identify for example whether following 1258, 1815, volcanic years in the models are preferentially selected for analogs.

In section 7 it is not clear to me why you have used the case with uniform white noise instead of the more realistic proxy noise setup, can you justify this? I would have thought that the most realistic set-up would be a better choice.

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Abstract. Assuming AM stands for analogue method, the definition should be moved to line 8 for clarity. “variants of the Analog Method (AM) …” And any mention of the “analog method” elsewhere in the text should be replaced with AM, please check the introduction especially.

Line 35 “to finally obtain a complete”

Line 41 “each gird-cell of”

line 70 and 72 – check brackets around references.

Line 179 – do you mean ensemble median? This is the most commonly used HadCRUT4 product…

Line 229 – the forcings are similar but not totally consistent i.e. different volcanic and solar forcing datasets are used. This should be mentioned and a citation to Schmidt et al 2012 added.

Line 244 – “HadCRUT4 dataset”

Lines 369-373 – Could a sentence be added here expanding why using the GISS model which has a lower variance would result in a stricter test. This wasn’t initially clear to me.

Line 417 “has the effect”

Line 473 “the effect of non-climate related”

RProxy PPE section – I would like to see a slightly expanded discussion of the degradation of results. To me this looks to be particularly prominent in the tropics where the proxy data has a poorer correlation to the observations. Is this correct?

Line 605 – The observations in the high Arctic are based on in-filled data and not real observations. Therefore the comparison of variance in models and observations in this region should be caveated.

Section 6. Could the improvement in performance of the screened network also be due to removing the proxies with poorer correlations with observations from the network?

Line 675 – This sentence is not clear.

Figure 7 – Why has the variance preservation plot log(σ/σ) not been shown as in figures 2,3,5,6? I think this would be useful to include.

Figure 11. Finding that the poles give the largest error is perhaps not that surprising given that this is the part of the world with the most variability. Could you add plots showing the errors divided by the models control variability in each grid cell as I think this would give a better demonstration of the performance of the AM.

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ED: Publish subject to minor revisions (review by Editor) (10 Apr 2017) by Joel Guiot

AR by Juan José Gómez-Navarro on behalf of the Authors (04 May 2017) Author's response Manuscript

ED: Publish as is (06 May 2017) by Joel Guiot

Short summary

This contribution aims at assessing to what extent the analogue method, a classic technique used in other branches of meteorology and climatology, can be used to perform gridded reconstructions of annual temperature based on the limited information from available but un-calibrated proxies spread across different locations of the world. We conclude that it is indeed possible, albeit with certain limitations that render the method comparable to more classic techniques.