cc: Keith Briffa , Eystein Jansen date: Mon, 18 Jul 2005 13:23:30 -0400 from: Tom Crowley subject: Re: thoughts and Figure for MWP box to: Jonathan Overpeck a few comments - 1) are you trying to choose between my way of presenting things and your way - ie, w w/out composite? 2) with your data, do they all go through from beginning to end? 3) why include chesapeake, which is likely a salinity record? 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 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 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 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. 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...THIS MAY NEED TO BE ADDRESSEDAS A GENERAL ISSUE SOMEWHERE (SHORTLY) IN YOUR DOC tom 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) > > >