date: Mon, 28 Apr 2003 14:46:11 +0100
from: Phil Jones <p.jones@uea.ac.uk>
subject: Fwd: Re: Fwd: RE: Rog Outline
to: k.briffa@uea.ac.uk,t.osborn@uea.ac.uk

    Somewhere in this message is Mike's review of the seasonal cycle paper.
    Phil

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     Date: Mon, 28 Apr 2003 09:02:43 -0400
     To: Phil Jones <p.jones@uea.ac.uk>
     From: "Michael E. Mann" <mann@virginia.edu>
     Subject: Re: Fwd: RE: Rog Outline
     Cc: mann@virginia.edu
     HI Phil,
     Re, DeFreitas--good to hear. That piece that Jim Salinger just forwarded is especially
     damning...
     Thanks for the message. I just got the record from Cronin before your email, so we're in
     pretty good shape. It would be nice if we can get the Briffa/Obsborn, Cook, and D'Arrigo
     et al series, but already we can do a reasaonble 2K composite. I've mostly been trying
     to seek out the long (2K) series so we can do the longer composite, but I suppose it
     would be useful to show a few key new records (especially tropical ones) that are
     shorter...
     I'm also working on filling in some details and preparing rought drafts of the various
     sections, so perhaps within a week we can merge what we have...
     Review on the JGR paper appended below. As you might imagine, my main sensitivity was w/
     conclusions about implications for e.g. Mann et al which I didn't think necessarily
     followed from this analysis. The revisions requested are mostly changes in wording, and
     it should be straightforward to address them in a final version...
     mike
     Comments:
      General Comments:
     This is an interesting manuscript, raising some  important issues regarding seasonality
     of past temperature trends that are interesting in there own right, and may have
     potential implications for certain paleoclimate reconstructions. These issues are worthy
     of discussion in the literature, and JGR is an appropriate venue. The authors, as is
     typical, have done a careful job with their analysis, and it appears sound, as do the
     primary conclusions, although I have some specific  reservations. The primary criticism
     is that the authors imply a greater generality to their conclusions than can actually be
     justified, given the limitations of the available data series. There are a number of
     important caveats that need to be invoked in the interpretation of the results, and the
     limitations in drawing large-scale conclusions from the limited data need to be
     acknowledged up front. There are a number of underlying issues regarding the nature of
     the seasonal and spatial details of past climate change (in particular, forced climate
     change) which likely impact the interpretation of the results, which are not given
     adequate discussion in the manuscript at present. Given the space available in a JGR
     paper (vs. e.g. a GRL article), there is no excuse for not providing more detailed
     discussion where appropriate.  I provide several specific comments below along these
     lines which should be addressed in a revised version of the manuscript.
     Specific Comments
     1) Abstract--the generality of the conclusions are overstated in the abstract. The
     evidence is only from Europe and China (i.e, only the fringes of the Eurasian continent
     alone) but the wording argues that implications apply to other regions. It isn't even
     clear that the conclusions apply to the interior of the Eurasian continent, let alone
     any of North America (see comments below). It is a leap of faith, then, to assume that
     the results generalize to extratropical hemispheric (let alone, full hemispheric)
     trends, and the authors need to be more cautious in drawing general conclusions.
     2) Introduction, first sentence: There is a potential "straw man" argument being
     introduced here. Precisely which "annual temperature" reconstructions are being referred
     to here? The statement made could arguably apply to Crowley and Lowery (2000), which is
     based on scaling a composite of largely extratropical (and mostly summer-sensitive)
     proxy records against the annual mean Northern Hemisphere mean instrumental series. It
     is far more difficult, however, to argue that the authors' statements fairly
     characterize the Mann et al (1998;1999)  annual mean temperature reconstruction. In the
     latter case, half of the area of the hemispheric mean surface temperature reconstruction
     comes from tropical latitudes (i.e., latitudes below 30N), and the proxy indicators
     primarily used to calibrate the tropical annual-mean patterns of variance are almost
     certainly not boreal warm-season in nature (for the example, the ENSO-scale patterns of
     tropical SST variance in the reconstruction are calibrated, in large part, by a
     combination of cold-season drought sensitive tree-ring data from Mexico, tropical
     tree-ring data, and tropical corals and ice cores--none of which could be argued to
     exhibit a boreal warm-season sensitivity bias!). The authors arguments cannot be argued
     to apply to these reconstructions (as seems to be implied by later comments--see below).
     3) Discussion of Figures 1 and 2 on pages 5-6:  the authors should compare a  single
     long-term composite series based on averaging the various (potentially, standardized)
     station JJA-DJF series with that which is available for the full NH back through the mid
     19th century. The point here is  to see how well they compare in terms of the general
     trends during the interval (back through the mid 19th century) of overlap--in fact,
     based on inspection of e.g. Figure 1, I don't think that there will be much similarity,
     and, if that is the case, then it demands extreme caution in generalizing about the true
     large-scale or hemispheric nature of inferred trends in summer-winter temperature
     differences based on the sparse long series available to the authors.
     4) Related to point #3 above, recent studies (see e.g. the discussion in the  Mann, 2002
     piece which is in the reference list but not actually cited in the text, and also the
     results of Shindell et al, 2003) have shown that large seasonal differences in
     temperature trends are expected in past centuries because of the seasonally-specific
     response, in particular, to volcanic forcing (see Kirchner et al, 1999). The largest
     seasonal differences are likely to occur in the continental centers, where volcanic
     forcing tends to impart a large summer cooling but also typically a sizeable
     dynamically-induced warming (related to the response of the Northern Annual Mode, or
     'AO' or 'NAO' to volcanic stratospheric aerosol forcing) in the following winter  The
     large differences, however, are observed over the continental centers, and in fringe
     regions such as Europe or China, the response may not even be of the same sign as the
     continental mean response, which is dominated by the behavior of the continental
     centers. Thus, any spatial network (proxy or instrumental) which exhibits a bias with
     respect to the sampling of the continents is likely to exhibit a bias in terms of the
     estimate of summer-winter temperature differences (Mann, 2002). Since the authors
     instrumental network only samples the fringes of the Eurasian continent, it is very
     unlikely to capture the true winter-summer difference in Eurasian continental mean
     temperature, let alone Northern Hemisphere extratropical continental (Eurasia and North
     America) temperature, let alone Northern Hemisphere extratropical mean (land and ocean)
     temperature, let alone true Northern Hemisphere (tropical and extratropical, land and
     ocean) temperature! Once again, this calls for caveats in the interpretation of the
     present results with regard to hemisphere-scale implications.
     5) Related to the above, why don't the authors show, in Figure 1, the results for some
     of the long available North American series (which includes several long east coast
     series, but also  a series in Minnesota back to the early 19th century) to establish the
     similarity of the longer-term summer-winter  trends in the two continents (this too
     should be included in the composite discussed in point #3 above).
     6) End of first paragraph on page 6, the authors might note that  certain modeling
     studies (Shindell et al, 2003) have indeed already looked at potential
     seasonally-distinct temperature changes in past centuries, that are associated with the
     seasonally-distinct signature of the response to known natural climate forcings.
     7) Figure 3 indicates a relationship that holds during the latter 20th century,
     presumably somewhat specific to the mix of internal and forced variability that
     dominates over that period. This may not be representative of the situation in earlier
     centuries, where the primary pattern of forced variability is by volcanic and solar
     forcing which impart distinct regional and seasonal signatures in the temperature field
     (see Shindell et al, 2001;2003) that are likely to be quite different from those
     associated with anthropogenic forcing (GHG and aerosol) which dominate during the
     interval examined by the authors. Related to this, have the series been detrended before
     calculating the correlations shown in Figure 3? This has a bearing on the
     interpretation.
     8) 3rd paragraph on page 7, the discussion of previous work (e.g. Mann et al, 1998;1999)
     here is misleading for the reasons spelled out in point #2 above.  The arguments
     assuming a warm-season sensitivity bias do not apply to the full hemispheric
     reconstruction but, at most, the extratropical component of the reconstruction. The
     statement  (2 sentences up from bottom of paragraph) "Their implicit assumption that the
     relative trends..." is not a fair statement in reference to the Mann et al multiproxy
     reconstructions, and the discussion needs to be revised here. An analysis (Rutherford et
     al, to be submitted) shows, using a common statistical method, but distinct data sets,
     that the multiproxy network of Mann et al calibrates and cross-validates cold-season
     variability more skillfully than the tree-ring maximum latewood density ('MXD') density
     network of Briffa and coworkers, while the Briffa et al MXD network, in turn, calibrates
     warm-season variance more skillfully than the multiproxy network.  In short, the
     conclusions drawn here don't apply to reconstructions of tropical surface temperature
     variability, nor to multiproxy data used to reconstruct that variability, so the
     implications of the authors results for multiproxy reconstructions of full Northern
     Hemisphere annual mean temperature  are not clear. The authors need to downplay their
     conclusions in this regard.
     9)  The authors and this reviewer are in common agreement that seasonally-specific
     biases are likely to be present in most climate proxy data, and that these biases need
     to closely considered in the process of climate reconstruction. This is a fair point,
     and one worth emphasizing in the conclusions But the specific conclusions of the authors
     in this study regarding summer-winter differences based on the series analyzed do not
     clearly generalize to other proxy-based surface temperature reconstructions
     (particularly multiproxy reconstructions with an equal tropical and extratropical
     emphasis) for the reasons spelled out above, and this point, in fairness, should be
     made.
     REFERENCES:
     Kirchner, I., G.L. Stenchikov, H.-F. Graf, A. Robock, and J.C. Antuna, Climate model
     simulation of winter warming and summer cooling following the 1991 Mount Pinatubo
     volcanic eruption, Journal of Geophysical Research, 104 (D16), 19039-19055, 1999.
     Shindell, D.T., Schmidt, G.A., Mann, M.E., Rind, D., Waple, A., Solar forcing of
     regional climate change during the Maunder Minimum, Science, 294, 2149-2152, 2001.
     Shindell, D.T., Schmidt, G.A., Miller, R., Mann, M.E., Volcanic and Solar forcing of
     "Little Ice Age" Surface Temperature Changes, Journal of Climate, in press, 2003.
     At 01:44 PM 4/28/2003 +0100, you wrote:

      Mike,
         Now had a chance to catch up a little.  On de Freitas I hope something is going to
     happen,
      but I don't to say anything yet. Hans and Clare will write to the publishers and try to
     get
      the reviews from de Freitas. Hans is now convinced he should go, but wants to do on a
     due
      cause basis and by the book so any backlash can be dealt with in a fair manner.
          I think I might have mentioned this to you in an email from Duke, but I must have
     done
      something wrong as I've lost some emails. I can't find the one from you saying you'd
     reviewed
      the recent JGR paper on the annual cycle, for example. I was bleary eyed at times at
     Duke,
      but I'm sure I read it !  Can you send the review if it's easy to locate ?
          On RoG all the series you've mentioned would be good to get. Tim is away here so I
      can't ask him if he's sent the Eurasian one, but I'll check when he's here. All the
     others
      seem good ones to go for. I'll email Dahl-Jenssen to see if I can get anything.
          As for the title, why don't we go for 'Climate during the past two millennia',
     still with the
      empahsis on the last one. This way it won't be too different from the one we gave to
     RoG.
      The first millennia will be semi quantitative and would just be smoothed versions -
     simple
      averages of what we can get, scaled against NH extended summers. We should probably
      put less emphasis on the MWP as Ray/Henry/Malcolm are working on that and more on
      the LIA in discussion - thinking aloud here. We could ask Ray for a draft in a couple
     of
      months and exchange bits of text.  I did think of Climate during the Christian Era !!!
     but that
      was going too far ! So, we will use AD and BC dates if needed, remembering AD goes
     before.
         At the EGS there was a 300 year coral series from Malindi, Kenya from Rob Dunbar
     that
      we should get. I'll email Rob if I can find his email address.
         Finally, I've written two sections on instrumental and documentary for section 2.
     Getting
      someone to type these in here and I'll work on them a bit before sending. I need to get
      Astrid's views on a few sentences on the Norse. Also I'll start a reference list as
     this might
      be a good way to start - who we must reference and also acknowledge.  When I began the
      writing I realised it wouldn't take too long as there isn't that much space. So
     Figures, Refs,
      Captions, Acknowledgements are crucial.
          Ed also has some Nepalese reconstructions - he's just got a paper in proof stage.
     They
      are not that long though, late 1500s. When he comes through you could ask him for those
      also.
      Cheers
      Phil
     At 16:59 26/04/03 -0400, you wrote:

     Hi Phil,
     I've managed to get my hands on the long chinese reconstruction, and have sent out
     requests for data to Ed Cook (the long RCS series from Esper et al), Tim (their long
     Eurasian reconstruction as published in the '99 Science piece--haven't hear from Tim
     yet, can you look into this?), D'Arrigo/Jacoby (Sol Dav Mongolia record) , and Cronin
     (Chesapeake Bay spring temperature reconstruction).  Ray apparently has been trying to
     get the Dye3/GRIP borehole data from Dahl-Jensen for some time, but without
     success--perhaps you could also try to get ahold of these?
     I'm going to make a preliminary attempt based on the few long (2K) records I already
     have (western U.S., China, Quelccaya o18, Fennoscandia) to use as a placeholder in the
     paper if nothing else, and we can improve on this as we get more data. Since we'll
     probably only want to form a composite at decadal resolution, we can probably scan many
     of the records if we haven't received them (I'm supporting an undergrad on a grant who,
     among other things, will be able to scan in series for us--they start in less than a
     month).
     let me know what you think. thanks,
     mike

     Date: Thu, 24 Apr 2003 13:59:28 -0400
     To: t.osborn@uea.ac.uk
     From: "Michael E. Mann" <mann@virginia.edu>
     Subject: Fwd: RE: Rog Outline
     Cc: p.jones@uea.ac.uk, mann@virginia.edu
     Tim,
     Can I get from you the Eurasian composite that you and Keith published in the Science
     perspective in '99? Phil and I are working on trying to do a simple-minded composite of
     a few of the 2K length temperature proxies for a piece we're working on together.
     thanks in advance for any help you can provide,
     mike

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     Date: Thu, 24 Apr 2003 11:14:26 +0100
     Sender: f028 <f028@uea.ac.uk>
     From: f028 <P.Jones@uea.ac.uk>
     To: "Michael E. Mann" <mann@virginia.edu>
     X-EXP32-SerialNo: 00104935
     Subject: RE: Rog Outline
     X-Mailer: InterChange (Hydra) SMTP v3.61.08
     Mike,
        Let's try and do this. I'll get back to you with more ideas next week.
      So for the moment, let's go with the last few or two millennia. I'll
      talk to a few who are here at Duke.
        Send revisions then assuming last few millennia, but the main emphasis
      will still be the last one.
      Cheers
      Phil

     ______________________________________________________________
                         Professor Michael E. Mann
                Department of Environmental Sciences, Clark Hall
                           University of Virginia
                          Charlottesville, VA 22903
     _______________________________________________________________________
     e-mail: mann@virginia.edu   Phone: (434) 924-7770   FAX: (434) 982-2137
              [1]http://www.evsc.virginia.edu/faculty/people/mann.shtml

     ______________________________________________________________
                         Professor Michael E. Mann
                Department of Environmental Sciences, Clark Hall
                           University of Virginia
                          Charlottesville, VA 22903
     _______________________________________________________________________
     e-mail: mann@virginia.edu   Phone: (434) 924-7770   FAX: (434) 982-2137
              [2]http://www.evsc.virginia.edu/faculty/people/mann.shtml

     Prof. Phil Jones
     Climatic Research Unit        Telephone +44 (0) 1603 592090
     School of Environmental Sciences    Fax +44 (0) 1603 507784
     University of East Anglia
     Norwich                          Email    p.jones@uea.ac.uk
     NR4 7TJ
     UK
     ----------------------------------------------------------------------------


     ______________________________________________________________
                         Professor Michael E. Mann
                Department of Environmental Sciences, Clark Hall
                           University of Virginia
                          Charlottesville, VA 22903
     _______________________________________________________________________
     e-mail: mann@virginia.edu   Phone: (434) 924-7770   FAX: (434) 982-2137
              [3]http://www.evsc.virginia.edu/faculty/people/mann.shtml

   Prof. Phil Jones
   Climatic Research Unit        Telephone +44 (0) 1603 592090
   School of Environmental Sciences    Fax +44 (0) 1603 507784
   University of East Anglia
   Norwich                          Email    p.jones@uea.ac.uk
   NR4 7TJ
   UK
   ----------------------------------------------------------------------------

