From	Keith Briffa	Date	Wed Jul 20 10:18:03 2005
To	Tim Osborn
Subject	Fwd: Re: thoughts and Figure for MWP box
Date: Tue, 19 Jul 2005 15:38:31 +0100 To: Tom Crowley , Jonathan Overpeck From: Keith Briffa Subject: Re: thoughts and Figure for MWP box Cc: Eystein Jansen 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/