date: Mon Jan 12 09:09:11 2004
from: Phil Jones <p.jones@uea.ac.uk>
subject: Re: Temperature reconstruction for the last millenium
to: Jorge Snchez Sesma <jsanchez@tlaloc.imta.mx>

    Dear Jorge,
        I addition to the comments I sent last week about people's preconceptions of the MWP
    and to a lesser extent the LIA, here are a few more on the paper.
    1. Greenland isn't inhospitable now nor in the 10th/11th centuries. The Inuit were there
   the
    whole time. Inhospitable to Europeans maybe, not to humans in general.
    2. The Goudie (1992) reference to trees growing north of where they do now in the 10-12th
    centuries needs to realise that trees will live happily north of where they are for the
   rest
    of their lives provided they have reached a certain size. In other words the warmth they
   needed
    only applies to a 30 year period when they germinated.
    3. Vineyards were still here in England during the 17th century - see below. They are here
    now - 7 times more than in 1086.
    4. It is best to see what the data says rather than put forward pre-conceptions. I suspect
   you
    have more faith in ECS than MBH because it is more in line with what you expect.
    5. Up to p4 in your paper, the only data that have been calibrated against instrumental
   data
    is the MBH series. All others are anecdotal.
    6. ECS is calibrated also, but against MBH - not against the instrumental data !  So, you
    can't say that MBH is wrong then use a data series developed by calibration against it.
   The
    reason for the differences between MBH and ECS has been discussed in the literature. ECS
    is more likely to be summer responsive and the sites are in mid-to-high latitudes compared
    to MBH. I'm attaching a paper that you might find relevant. It relates to possible changes
    in the seasonal cycle.
    7. The main problem with the paper, though, is that the ice-core acidity series you use is
    a forcing series (i.e indicative of volcanic activity) and not a response series (i.e
   temperature
    in its simplest form).  Your calibration is based on a low-frequency relationship. There
   will
    be few degrees of freedom after the smoothing.
    8. MRBHK have done a lot more to the borehole record than Huang et al (2000) like.
    Also it too is calibrated against MBH. It isn't just an interpolation of the original
   data.
    9. You can't choose ECS just because it has more variability than MBH.
    10. Finally, just because a warming began 400 years ago doesn't mean that it is all due
    to the same cause. It was obviously natural until the 20th century, but this doesn't
    preclude it being human-induced during the last century.
    One small point, on p3 line 7 of the first para of Background, sea should be sea ice. It
   took me
   a while to realise what you must mean here.
    Cheers
    Phil


    Dear Jorge,
       I will look through the paper when I am away from CRU either next week or the week
    after. I see you mention vineyards as far north as York in the MWP. This has very little
    to do with climate change - there is a vineyard near there today. Here is some text I
   wrote
    a while ago about two anecdotes, the Thames freezing and vines in York.
   1) River Thames freeze-overs (and sometimes frost fairs) only occurred 22 times between
   1408 and 1814 [Lamb, 1977] when the old London Bridge constricted flow through its multiple
   piers and restricted the tide with a weir. After the Bridge was replaced in the 1830s the
   tide came further upstream and freezes no longer occurred, despite a number of
   exceptionally cold winters. 1962/3, for example, was the third coldest in the Central
   England Temperature (CET) record [the longest instrumental record anywhere in the world
   extending back to 1659, Manley, 1974; Parker et al., 1992], yet the river only froze
   upstream of the present tidal limit at Teddington. The CET record clearly indicates that
   Thames (London) 'frost fairs' provide a biased account of British climate changes (let
   alone larger-scale changes, see Figure 2c) in past centuries.

   2) Monks in Medieval England grew vines as wine was required for the sacrament. With
   careful husbandry vines can be grown today and indeed vineyards are found as far north as
   southern Yorkshire. There are a considerably greater number of active vineyards in England
   and Wales today (roughly 350) than recorded during Medieval times (52 in the Domesday Book
   of AD 1086), exposing as distinctly curious the claims sometimes made that evidence of vine
   growing in Medieval England provides evidence of unusual warmth at that time. Vine growing
   persisted in England throughout the millennium. The process of making sparkling wine was
   developed in London (by Christopher Merret) in the 17th century, fully 30 years before it
   began in the Champagne region of France. Thus, the oft-cited example of past vine growing
   in England thus reflects little, if any, on the relative climate changes in the region
   since Medieval times.
      Also, vine growing was mainly at monasteries. Because the Romans and the Normans came
    from the south they brought vines with them. The population that was here at the time of
    the invasions were Celts when the Romans came and Anglo-Saxons and Celts when the
    Normans came. Neither of these two peoples drank wine and this is also a factor in why
    vine growing was never popular.
      Most of the above comes from the web site of the English vine growing association.
   Vineyards
    have produced wine throughout the millennium.   As most of the monasteries were
    destroyed by Henry the 8th in 16th century most of the vineyards fell into disrepair.
   There
    were vineyards around London in the 17th century.
    Cheers
    Phil
   At 15:36 05/01/2004 -0600, you wrote:

     Dear Dr Jones:
     You will find attached a very crude draft of a paper about Global
     Temperature reconstruction. This reconstruction have a notable coincidence
     with recent publication (Esper, Cook and Shweingruber 2002).
     I would like to know your oppinion and suggestions to improve the text
     before to be sent this paper to Science.
     I would like to emphasize that I continue to be interested to visit CRU and
     stablish a formal collaboration in this subject.
     My best regards,
     Jorge Snchez-Sesma
     Instituto Mexicano de Tecnologa del Agua
     Subcoordinacin de Hidrometeorologa
     Paseo Cuauhnahuac No. 8532, Col. Progreso
     Jiutepec, Morelos
     62550, Mxico
     telefono:       52+(777)329-3600 x 879
     fax             52+(777)3293683
     email:          jsanchez@tlaloc.imta.mx
     pagina: [1]http://nimbus.imta.mx

   Prof. Phil Jones
   Climatic Research Unit        Telephone +44 (0) 1603 592090
   School of Environmental Sciences    Fax +44 (0) 1603 507784
   University of East Anglia
   Norwich                          Email    p.jones@uea.ac.uk
   NR4 7TJ
   UK
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