date: Fri Jul 11 17:27:35 2008 from: Keith Briffa subject: Re: URGENT: Review of Nature manuscript 2008-05-04767A to: f.fornasier@nature.com Faye things have been very hectic for me and I am sorry it has taken some time to do this . I have really had to study it and several associated papers before coming to this conclusion. My overall opinion is reject. There is little I believe that is significant here , and a lot of implied significance and absence of clear interpretation of the results. There is also a "new" approach to processing data hidden in the supplementary material but this is not relevant to the substance of the paper as the later processing negates the need to use it in the end anyway. The following section may be copied to the authors but I prefer to remain anonymous . I appreciate your offer to copy this review into the system for me - as I am really overloaded with stuff, I accept. Please acknowledge receipt thanks again Keith ------------------------------------------------------------------------------------------- ---------------------------------------------------------------- Comments to be passed to the authors on Non-uniform interhemispheric temperature trends over the past 550 years By R. Duncan et al The basic message proposed by the authors in this manuscript is that the Northern Hemisphere mean annual temperature varies, largely out of phase, with annual average Southern Hemisphere temperatures on a characteristic timescale of about 30-60 years. One might query whether this is saying much of interest, but the authors couch this result in the context of statements about the roles of natural versus anthropogenically driven inter-hemispheric temperature differences. If the paper was to provide insight into the specific role of tropospheric aerosols and the validity of the way they have been included in IPCC AR4 models to achieve greater consistency between observed temperatures and forced GCM model experiments then this would provide a strong case for publication. However, I do not feel that the manuscript does anything like this . Nor does the manuscript really confirm that an understanding of the workings of the IPO or AMO are critical for understanding and modelling future climate changes to any greater degree than was already understood on the basis of instrumental analyses or model experiments. The primary mode of instrumental temperature variability across both the North and South Hemispheres over the 20^th century, comprises the 3-stage wide-scale warming illustrated in Figures 1 and 2 of Parker et al. (2007). Understanding of regional and decadal-scale differences in temperature changes over land and ocean and between North and South are relevant for framing uncertainties in attribution studies and projections of likely warming rates, their significance on decadal scales should not be overstated. For example, the variance explained by the AMO and IPO in large-scale analyses of instrumental temperature variability in the 20^th century is on the order of a few per cent (e.g. Parker et al., 2007). This paper is not able to advance our understanding of the causes or even quantify the changing amplitude of the IPO or AMO or the net effect of their combined influence over time. Looking at the new data the authors present, it is not clear to me that the evidence for out of phase cycling between the Northern Hemisphere reconstructions and the New Zealand reconstructions is particularly strong or constant over the whole length of the series. Any (even white-noise) bandpass filtered data series , when superimposed, would show periods of in phase and out of phase behaviour. The series shown by the authors are out of phase sometimes and not at others. We can deduce little about the past behaviour of the IPO or AMO for either circumstance. The characterisation of the dominant multi-decadal patterns of variability of the so-called IPO varies in spatial signature and temporal importance depending on whether SST or NMAT data are used as the basis data set (e.g. see Figure 3 of Parker et al., 2007 quoted by authors). Regardless of which are used the relationships between New Zealand temperature variations and temperatures in other parts of the Southern Hemisphere, associated with changing IPO status are complex (and possibly seasonally dependent). This suggests that using New Zealand as a surrogate for mean Southern Hemisphere temperatures on the decadal timescale, may be unfounded. The authors imply that their data are being used to imply details of contrasting temperature trends between the northern and southern hemispheres and that these data are the only data available to compare against the northern hemisphere average data. While it is true that instrumental data show the AMO and IPO to be negatively correlated with New Zealand temperatures, temperatures in other areas of the Southern Hemisphere are not. The authors do not present a formal phase analysis or, for that matter, compare their New Zealand bandpassed data with those from temperature series representing other regions of the Southern Hemisphere that do exist (in South America, Tasmania and even New Zealand i.e. as published by Cook and colleagues). The work by Cook has specifically pointed out a characteristic peak in the variance spectrum at around 30-60 years in Tasmanian temperature and he carried out an analysis of its changing significance through time using singular spectrum analysis. A similar detailed formal comparison of the covariance between the various available Southern Hemisphere data (and the Northern Hemisphere data) seems justified. Personally, I consider the plots of the Wavelet spectra shown in Supplementary Figure 1 of little value in this regard. It is true that Figure 2 of the manuscript, at first sight, appears to show an intriguing, even compelling, correlation between the series representing the sum of the IPO and AMO and the Northern Hemisphere/New Zealand temperature difference (specifically Figure 2c). However, previous analyses of instrumental data show New Zealand temperatures to be negatively correlated with each of (and so also the sum of ) the IPO and AMO. As these modes describe contrasting temperatures in the North and South Hemispheres it is to be expected that the Northern Hemisphere minus New Zealand temperature ( or estimated temperature fitted against it) will correlate positively . In summary I just can not see that there is enough new information or new insight provided in this manuscript to support publication. ------------------------------------------------------------------------------------------- ------------------------------------------------------------------ At 11:33 08/07/2008, you wrote: Content-Disposition: inline Content-Length: 1187 Content-Transfer-Encoding: binary Content-Type: text/plain Dear Professor Briffa I am writing in reference to the manuscript by Dr Duncan and co-authors entitled Non-uniform interhemispheric temperature trends over the past 550 years.. It has now been a number of weeks since we sent this manuscript to you for your comments, but we have not yet received your review. Your comments on this manuscript are valued; however, it is of the utmost importance that we receive them as soon as possible to prevent any further delay in making a decision on this manuscript. You can view the manuscript and complete the review form by clicking on the link below: <[1]http://mts-nature.nature.com/cgi-bin/main.plex?el=A5K1CWs3A7fHu6J2A9roFjn4Z8ixN3Vtrd hAsjAZ> Alternatively, if it would be more convenient, you may send your review directly to me by return email. In this case, please highlight which comments are confidential and which should be passed on to the authors. General information for peer-reviewers is at [2]www.nature.com/nature/authors/referees/index.html. We look forward to receiving your comments very soon. Yours sincerely Faye Fornasier Staff Nature This email has been sent through the NPG Manuscript Tracking System NY-610A-NPG&MTS -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 [3]http://www.cru.uea.ac.uk/cru/people/briffa/