From: Keith Briffa <k.briffa@uea.ac.uk>
To: Tim Osborn <t.osborn@uea.ac.uk>
Subject: Fwd: Re: thoughts and Figure for MWP box
Date: Wed Jul 20 10:18:03 2005

     Date: Tue, 19 Jul 2005 15:38:31 +0100
     To: Tom Crowley <tcrowley@duke.edu>, Jonathan Overpeck <jto@u.arizona.edu>
     From: Keith Briffa <k.briffa@uea.ac.uk>
     Subject: Re: thoughts and Figure for MWP box
     Cc: Eystein Jansen <eystein.jansen@geo.uib.no>
     Tom et al
     thanks for remarks - in response to Tom's questions
     At 18:23 18/07/2005, Tom Crowley wrote:

     a few comments -
     1) are you trying to choose between my way of presenting things and your way - ie, w
     w/out composite?

     Yes

     2) with your data, do they all go through from beginning to end?

     pretty much - and have been standardised over the maximum period for each (not
     necessarily the best way?)

     3) why include chesapeake, which is likely a salinity record?

     Because Moberg used it in their latest reconstruction - I agree that I would not use it
     because of the dubious temperature signal (salinity effect and no local replication) and
     poor dating control (and I do not like the way the Moberg method effectively over
     weights the low-frequency predictor series in their analysis).

     4) some of your data are from virtually the same site - Mangazeja and yamal are both w.
     siberia - I composited data available from multiple sites to produce one time series,
     which is equally counted against the other regions, which might (greenland, w.U.S., e.
     Asia) or might not have multiple records in them

     Just to reiterate - I understood after the group chat with Susan S. in Beijing , that we
     were being asked  to try to produce a "cloud" diagram including as many of "original"
     predictor series ,from all the reconstructions, to see if it provided an "obvious"
     picture of the unprecedented warming over the last millennium or so. Tim and I are in no
     way trying t produce a different Figure for the sake of producing a different Figure .
     In practice this is hard to do (because some records are sensible "local" composites
     already, and how far do you go in showing all input data? The problem of what and how to
     composite is tricky - and no obviously "correct"  way is apparent.
     Having said this , Tom's way is fine with me (provided the composites are robust) and we
     get general agreement. Am happy to go with Tom's Figure , or version that incorporates
     as many records as possible - but as we have said - without the composite or temperature
     scaled add ons.

     5) I am not sure whether it is wise to add me to the CA list, just because the reviewer
     is supposed to be impartial and a CA loses that appearance of impartiality if he has now
     been included as a CA - may want to check with Susan S. on this one to be sure - still
     happy to provide advice

     My own position on this is that you are an "unofficial" referee, who has (and still is)
     making a significant contribution - I see no conflict

     6) I am happy to go in either direction - include or not include my figure - all I need
     are specific directions as to what to do, as CLAs you people need to decide, and then
     just tell me what or what not to do

     Agree - CLAs please rule on the individual record/composite question - I am very happy
     to go with Tom's Figure. We did ours because we were asked to.

     7) I am a little unhappy with the emphasis on hemispheric warmth - lets face it, almost
     all of the long records are from 30-90N - the question is:  how representative is 30-90N
     to the rest of the world?  for the 20th c. one can do correlations with the instrumental
     record, but co2 has almost certainly increased the correlation scale beyond what it was
     preanthropogenic.

     Absolutely agree , and hope this comes over in text (and bullets) - if not needs
     strengthening (note David R's comments).

      you could correlate with quelcaya - not  sure how many other records there are that are
     annual resolution - in the tropics I have produced a tropical composite (corals +
     Quelc.) but it only goes back to ~1780 - corals just don't live v long - in that
     interval at least the agreement is satisfactory with the mid latitude reconstruction but
     there is only 100 years extra of independent information beyond the instrumental
     record..

     We have gone round in circles over this , but understand consensus to be that Quelc. not
     a clean temperature record. Agree corals would be better longer (the new coral-based
     reconstruction by Rob Wilson et al
     goes back to 1700 and shows unprecedented tropical warming . Along with the text from
     Julie we can not go much further, but the importance of extending the tropical (and SH
     records needs to be very clear)

     .THIS MAY NEED TO BE ADDRESSEDAS A GENERAL ISSUE SOMEWHERE (SHORTLY) IN YOUR DOC

     Really hope it is already - but advise if you think not

     tom

     Thanks for this - lets take lead from J and E now  (also can you advise on state of play
     with the Hegerl et al manuscript?)
     thanks
     Keith

     Jonathan Overpeck wrote:

     Hi Keith, Eystein and Tom: See below (BOLD) for my comments. Thanks for moving this
     forward and making sure we do it right (i.e., without any bias, or perception of bias).

     Dear Peck, Eystein and Tom
     At this point we thought it was important to review where we think we are with the MWP
     Figure.
     First, we have no objection to a Figure . Our only concerns have been that we should
     1/... be clear what we wish this Figure to illustrate (in the specific context of the
     MWP box) - note that this is very different from trying to produce a Figure in such a
     way as to bias what it says (I am not suggesting that we are, but we have to guard
     against any later charge that we did this). We say this because there are intonations in
     some of Peck's previous messages  that he wishes to "nail" the MWP - i.e. this could be
     interpreted as trying to say there was no such thing, and

     SORRY TO SCARE YOU. I **ABSOLUTELY** AGREE THAT WE MUST AVOID ANY BIAS OR PERCEPTION OF
     BIAS. MY COMMENT ON "NAILING" WAS MADE TO MEAN THAT ININFORMED PEOPLE KEEPING COMING
     BACK TO THE MWP, AND DESCRIBING IT FOR WHAT I BELIEVE IT WASN'T. OUR JOB IS TO MAKE IT
     CLEAR WHAT IT WAS WITHIN THE LIMITS OF THE DATA. IF THE DATA ARE NOT CLEAR, THEN WE HAVE
     TO BE NOT CLEAR. THAT SAID, I THINK TOM'S FIGURE CAPTURED WHAT I HAVE SENSED IS THE MWP
     FOR A LONG TIME, AND BASED ON OTHER SOURCES OF INFO - INCLUDING KEITH'S PROSE. THE IDEA
     OF A FIGURE, IS THAT FIGURES CAN BE MORE COMPELLING AND CONNECT BETTER THAN TEXT. ALSO,
     THERE ARE MANY WAYS TO LOOK AT THE MWP, AND AS LONG AS WE DON'T INTRODUCE BIAS OR
     ANYTHING ELSE THAT WILL DILUTE THE MESSAGE IN THE END, THE IDEA IS TO SHOW THE MWP IN
     MORE WAYS THAN TWO (THAT IS, THE EXISTING FIGS IN THE TEXT THAT KEITH AND TIM MADE).

      2/ ...agree that we have done this in the best way.
     The truth is that there IS a period of relative warmth around the end of the 1st and
     start of the 2nd millennium C.E. , but that there are much fewer data to base this
     conclusion on (and hence the uncertainty around even our multiple calibrated multi-proxy
     reconstructions are wide). The geographical spread of data also impart a northern (and
     land) bias in our early proxy data.

     NEED TO BE CLEAR ABOUT THIS BIAS IN THE CAPTION AND BOX TEXT

     My understanding of Tom's rationale with the Figure is that we should show how, because
     the timing of maximum pre-20th century warmth is different in different records, the
     magnitude of the warmest period (for the Hemisphere , or globe, as a whole) is less than
     the recently observed warmth.

     YES, BUT IN A WAY THAT SAYS "LOOK, HERE ARE THE ACTUAL REGIONAL CURVES - CHECK IT OUT
     FOR YOURSELF" INSTEAD OF JUST SAYING (IN A SCIENTIFICALLY MORE STANDARD MANNER - HERE
     ARE THE VARIOUS, MOST ROBUST, LARGE AREA RECONSTRUCTIONS. IN MY MIND, THE LATTER
     (KEITH/TIM FIGS IN THE MAIN TEXT) WILL BE THE MOST APPEALING/CONVINCING TO PALEOCLIMATE
     SCIENTISTS, BUT TOM'S MIGHT HELP THERE, AND CERTAINLY WITH NON-PALEO SCIENTISTS AND
     POLICY FOLKS. MIGHT HELP... IF IT DOESN'T NOTHING LOST, BUT IF IT COULD HURT CONVEYING
     UNDERSTANDING, THEN ITS BAD TO USE THE NEW FIGURE.

     The reconstructions we plot in Chapter 6 already express the mean Hemispheric warmth
     (after various selection and scaling of data), and so the additional information that
     the MWP box figure should show must relate to the scatter of the proxy data. There seems
     to be a consensus that this is best done by showing individual records , and we are
     happy to agree.
     What we worry very much about, however, is that we should not produce a Figure that then
     conflicts with the picture of proxy evidence for Hemispheric mean warmth as a
     whole,shown in the main Chapter Figure. By showing a composite (as Tom has done) and
     scaling against another (30-90degrees N) temperature record - this is just what is done.

     ABSOLUTELY RIGHT - CAN'T HAVE CONFLICT.

     As we promised, Tim has produced a similar Figure, using the same series plus a few
     extras, but omitting the composite mean and the scaling against instrumental
     temperatures. The idea was to include as many of the original input series (to the
     various reconstructions) as we could  - though avoiding conflicting use of different
     versions of the same data. The precise selection of records will have to be agreed and,
     presumably, based on some clear, objective criteria that we would need to justify (this
     will not be straight forward). This, along with Tom's plot (forwarded by Peck) is in the
     attachment.
     We would like to get your opinion now, and especially Tom's, on the points regarding the
     composite and scaling. We would be in favour of just showing the series - but do they
     make the point (and emphasise the message of the text in the box)? Or does the scatter
     of the various series as plotted, dilute the message about the strength of 20th century
     mean warming (note the apparently greater scatter in the 20th century in our figure than
     in Tom's)? Can you all chip in here please.
     best wishes

     WHAT ABOUT THE IDEA THAT WE ONLY SHOW THE SERIES FOR THE MWP, SINCE THE COMPARISON TO
     THE 20TH CENTURY IS DONE WELL (AND BEST?) IN THE TEXT FIGS (WHICH I'M ATTACHING JUST IN
     CASE TOM DOESN'T HAVE, ALONG WITH THE TEXT - IF YOU HAVE TIME, TOM, PLEASE READ COMMENT
     ON ANYTHING YOU WISH, BUT CERTAINLY THE LAST 2000 YEARS BIT - ASSUME YOU'LL BE DOING
     THIS AT THE REVIEW STAGE ANYHOW...)
     ANOTHER THING THAT IS A REAL ISSUE IS SHOWING SOME OF THE TREE-RING DATA FOR THE PERIOD
     AFTER 1950. BASED ON THE LITERATURE, WE KNOW THESE ARE BIASED - RIGHT? SO SHOULD WE SAY
     THAT'S THE REASON THEY ARE NOT SHOWN? OF COURSE, IF WE ONLY PLOT THE FIG FROM CA 800 TO
     1400 AD, IT WOULD DO WHAT WE WANT, FOCUS ON THE MWP ONLY - THE TOPIC OF THE BOX - AND
     SHOW THAT THERE WERE NOT ANY PERIODS WHEN ALL THE RECORDS ALL SHOWED WARMTH - I.E., OF
     THE KIND WE'RE EXPERIENCING NOW.
     TWO CENTS WORTH

     Keith and Tim
     P.S. We agreed in Beijing that we should definitely ask Tom to be a CA .

     TRUE - BUT HAS ANYONE CONFIRMED W/ TOM. TOM, YOU OK W/ THIS?
     THANKS - A GREAT DISCUSSION, AND LETS SAY THE JURY IS STILL OUT ON THIS FIGURE UNTIL WE
     ALL ARE COMFORTABLE WITH WHAT IT LOOKS LIKE IN THE END.
     BEST, PECK

     --
     Professor Keith Briffa,
     Climatic Research Unit
     University of East Anglia
     Norwich, NR4 7TJ, U.K.
     Phone: +44-1603-593909
     Fax: +44-1603-507784
     Attachment converted: Macintosh HD:mwpbox_figures.pdf (PDF /«IC») (0008A8AE)

     --
     Professor Keith Briffa,
     Climatic Research Unit
     University of East Anglia
     Norwich, NR4 7TJ, U.K.

     Phone: +44-1603-593909
     Fax: +44-1603-507784
     [1]http://www.cru.uea.ac.uk/cru/people/briffa/

   --
   Professor Keith Briffa,
   Climatic Research Unit
   University of East Anglia
   Norwich, NR4 7TJ, U.K.

   Phone: +44-1603-593909
   Fax: +44-1603-507784
   [2]http://www.cru.uea.ac.uk/cru/people/briffa/

References

   1. http://www.cru.uea.ac.uk/cru/people/briffa/
   2. http://www.cru.uea.ac.uk/cru/people/briffa/

