From: SCHLOERER@rzmain.rz.uni-ulm.de (Jan Schloerer)
Subject: Re: Who is Sallie Baliunas
Date: 11 May 1995 20:26:56 GMT
Message-ID: <3otrug$g7g@waage.rz.uni-ulm.de>

moore@Hoover.Stanford.EDU   (Tom Moore)  writes :
> SCHLOERER@rzmain.rz.uni-ulm.de (Jan Schloerer) writes:
>>  I predict that within six months Tom Moore will once again tell us
>>  that the modest medieval warming is a nice analog for greenhouse gas
>>  induced climatic change, even though it probably was neither a global
>>  nor a year-round phenomenon.  Never mind ;-)
>
> The evidence is that it was a year round warming.  It is not as clear
> that it effected the southern hemisphere, but all of the northern
> hemisphere was warmed.   The earlier warming around 3,000 to 7,000
> years ago also appears to have included all of the northern hemisphere
> and while the evidence is not as strong appears to have warmed both
> winters and summers.   The evidence that both periods warmed the whole
> globe comes from the rise in sea levels experienced during both periods.

Prediction fulfilled.  If only predicting lotto figures were that easy ;-)

More seriously, I see two possibilities:  Tom Moore may have missed
quite a few posts this February, or he may ignore any information that
doesn't support his opinions.  For the moment, I assume the former.
To ensure that Tom Moore gets what follows, I will email it to him.
I apologize for shamelessly quoting from old postings, time is scarce.

My "prediction" was about the Medieval Warming Epoch.  Thus I won't
address the Holocene Optimum roughly 6000 years ago in detail, which
may indeed have entailed some year-round warming, and which may indeed
have been a global phenomenon, even though it probably was  *mainly*
a summer phenomenon over Northern Hemisphere land areas [1].

According to the information available to me   -   which is more
recent than the sources employed by Tom Moore, like Lamb's famous but
now dated books   -   the so-called Medieval Warm Period was probably
*not*  a global phenomenon.  In the Northern Hemisphere, as far as
it went, it was mainly a summer phenomenon.

Quote from [2], page 55,  *emphasis*  mine,  refs upon request.  These
authors, a group including several highly respected paleoclimatologists,
are well aware of Lamb's work.  They just have found out some more
details since.

    "Medieval Warm Epoch (ca. A.D. 1000 to 1300)"

    "Historical records from Eurasia demonstrate that the Medieval
    period (A.D. 1000 to 1300) was a period of relative warmth there
    (LeRoy Ladurie 1967; Lamb 1965, 1988; Alexandre 1987; Bradley 1992).
    The exact dates are uncertain, but A.D. 1120 to 1280 bracket part
    of the warm time.  The dates listed in the subheading come from
    Lamb (1965), who defined the period as a  `prevailing warm epoch
    with dry anticyclonic character, especially in summer ... between
    A.D. 1000 and 1300'  (for Europe).   *Summer*  temperatures in
    *some regions*  may have been  1 o  to  1.5 o C  higher than they
    are at present.  Tree-ring records from Scandinavia (Briffa et al.
    1990) and the Northern Ural Mountains (Graybill and Shiyatov 1992)
    show evidence of warmer summer temperatures.  The global extent of
    the higher-than-present temperatures is still unknown (Webb 1991),
    however, and Bradley (1992) concludes that  `the available evidence
    suggests that there was  *not*  a long, continuous warm interval
    which was synchronous throughout the world, or even throughout the
    Northern Hemisphere.'   Further study of historical and other
    records is strongly encouraged in order to broaden the data base
    available for this period."

Quote from [3], abstract, kindly provided by William Connolley
(wmc@unixa.nerc-keyworth.ac.uk).  So far, interlib loan has not
turned up the paper, and this is all I know about this article,
which forms the introduction to the March 1994 issue of the journal
Climatic Change, devoted to the so-called Medieval Warm Period.

    [cut]   "Our review indicates that for some areas of the globe
    (for example, Scandinavia, China, Sierra Nevada in California,
    the Canadian Rockies and Tasmania),  temperatures, particularly in
    summer, appear to have been higher during some parts of this period
    than those that were to prevail until the most recent decades of the
    20th C.  These warmer regional episodes were not strongly synchronous.
    Evidence from other regions (for example, the SE US, S. Europe along
    the Med., and parts of S. America) indicates that the climate during
    that time was little different to that of later times, or that the
    warming, if it occured, was recorded at a later time than has been
    assumed.  Taken together, the evidence does not support a *global*
    Medieval Warm Period."    [cut]

For those who may not yet know:  The researchers [2] unanimously
rejected the use of past warm periods as analogs for greenhouse gas
induced climatic change.  For each of the candidate warm periods known
so far, they gave specific reasons why it doesn't fit the bill.


[1] Thomas J. Crowley,  Gerald R. North,  Paleoclimatology
    Oxford Univ. Press, New York, USA 1991
    Especially sections 3.3 and 4.5
[2] T. Webb III (Rapporteur),  T.J. Crowley,  B. Frenzel,  A.-K.
    Gliemeroth,  J. Jouzel,  L. Labeyrie,  I.C. Prentice,  D. Rind,
    W.F. Ruddiman,  M. Sarnthein,  A. Zwick,       Group Report:
    Use of paleoclimatic data as analogs for understanding future
    global changes.    Pages 50-71 in:  J.A. Eddy  and  H. Oeschger
    (eds),   Global Changes in the Perspective of the Past.
    Chichester, UK, Wiley 1993
[3] M.K. Hughes  &  H.F. Diaz,
    Was there a medieval warm period, and if so, where and when ?
    Climatic Change 26 (March 1994), 109-142


Jan Schloerer                    schloerer@rzmain.rz.uni-ulm.de
Uni Ulm     Klinische Dokumentation     D-89070 Ulm     Germany