Wednesday, May 2, 2012

3718.txt

cc: Eystein Jansen <eystein.jansenatXYZxyz.uib.no>, Tom Crowley <tcrowleyatXYZxyze.edu>
date: Mon, 18 Jul 2005 10:58:09 -0600
from: Jonathan Overpeck <jtoatXYZxyzrizona.edu>
subject: Re: thoughts and Figure for MWP box
to: Keith Briffa <k.briffaatXYZxyz.ac.uk>

<x-flowed>
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)


--
Jonathan T. Overpeck
Director, Institute for the Study of Planet Earth
Professor, Department of Geosciences
Professor, Department of Atmospheric Sciences

Mail and Fedex Address:

Institute for the Study of Planet Earth
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Tucson, AZ 85721
direct tel: +1 520 622-9065
fax: +1 520 792-8795
http://www.geo.arizona.edu/
http://www.ispe.arizona.edu/
</x-flowed>

Attachment Converted: "c:\eudora\attach\Ch06_FOD_11_text1.doc"

Attachment Converted: "c:\eudora\attach\Ch06_FOD_11_figures2.doc"

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