date: Thu Oct 12 15:41:00 2000
from: Keith Briffa <k.briffa@uea.ac.uk>
subject: Re: Holocene paper
to: f055 <T.Osborn@uea.ac.uk>

   Hi Tim
   Glad you there and already up and running (or at least striding purposefully) . First, no,
   the part one paper has not had it's final few changes - but I have spoken to John Matthews
   and he will handle the refereeing. Saying it has been submitted is not an inexactitude . It
   has been submitted to the guest editor (me) . The changes are so small that they can be
   done at post-referee stage. I shall therefore send it to Matthews .
   Part 2 , needs more work . We will do this after HIHOL.
   I have looked at the plots and shown them to Phil and we have both considered your message
   and the points you raise.
   Phil thinks you should re-plot the maps to make the zero more obvious  -  (use the colour
   currently indicating -0.4 to -0.6 as the zero band and shift the spectrum along ). The
   winter warming over land in recent decades is clear, though the large area of slightly
   warmer ocean compensates remarkably. In fact, I am surprised at the general concurrence
   between the winter and summer curves. One wonders at what level of spatial coverage this
   begins to break down. The anomalies in the first two decades are not that obvious as to
   indicate a clear regional bias , and it could well be that your suggestion of the poor
   spatial coverage causing the difference might be true. Phil suggested you do the frozen
   grid ( coverage of 1870s/80s) to redo the time series and I suggest you could do it also
   for the land only . The work by Chenoworth is pretty convincing that there is indeed bias
   in early western US records but this is not where you see it - in fact, your early summer
   warmth is as much a marine phenomenon.( and I for one am sceptical about the lack of
   exposure problems in the very early Scandinavian summer temperatures that Phil has
   assembled. We  note also that areas of ocean coverage appear relatively green (summer
   warmer) right through to the present. It is possible that there is a problem with the
   marine temperature records?
   We don't think that you can resolve this easily and we wonder why the extra 20 years will
   make such a difference - if short of data , calibrate always on the early and verify on the
   later.  Do you have a phone where I can ring you? I am in turmoil here ( yes even more so
   than normal) because I started to move a few thing over to my new room. After a full 2 days
   , we (Phil also decided to sort out a few things!) I believe we have filled a skip but
   there is no discernable gain of space in any of the 3 rooms.
   At 10:07 PM 10/11/00 +0100, you wrote:

     Keith,
     well, got here ok.
     Not much to do today as Mike is lecturing and his post-doc is away (but only
     for today).
     I think they have IDL, which will help speed things up a bit.
     The main question I have is about the Holocene paper - I've got a copy for
     Mike, but wanted to know
     the status of it.  Have you made any of the Russian's modifications (mainly
     additional references)?
     We really need to get the review process going - I've told Mike that it is
     submitted.
     Even though it's got to wait for the special issue before it appears, it'd be
     good to be able to say soon
     that it is "in press" rather than just submitted.  I haven't brought a copy of
     the part II Holocene paper,
     but I will be explaining what we've done - have you made any progress with
     that one recently?  I
     remember that you were hoping to, but HIHOL etc. may have got in the way.
     I've been taking a look at the supposedly biased early warmth in the
     instrumental summer records,
     while Mike is busy this afternoon (you know we cut off at about 1871, because
     it is too warm before
     that).  Because we're using summer and MXD, we have to restrict ourselves to
     an 1881-1960
     calibration period.  But, if we're going to try Mike Mann's method then we
     need a longer period
     for calibration/verification etc., so this needs to be solved if possible...
     hence my look at it.
     I've computed Apr-Sep means and Oct-Mar means from the gridded temperature
     dataset, and also
     differenced them (Apr-Sep minus Oct-Mar) on a grid box basis.  The Northern
     Hemisphere mean
     timeseries and differences, and decade-by-decade maps of the gridded
     differences, should be on
     the colour laser printer for you to look at (3 pages in all).  The NH
     difference time series shows a
     marked jump, or maybe a trend, prior to about 1900 (they look different to the
     results Craig got,
     but he has been looking at the amplitude of the annual harmonic, which is
     different to the difference between
     two 6-month means done here).  I though that the maps might show the warm bias
     coming from
     just a small number of biased grid points.  The screen here isn't working
     quite right, but I think the
     maps show that most of Europe was positive (summer warm relative to winter)
     during
     the 1860s and subsequent decades,  with a single highly positive box in west
     US in the 1860s, and
     additional ones coming in in subsequent decades.  Could you have a look at
     these and show them
     to Phil?  It really needs to be sorted out as to whether these are real or
     artefacts.  Perhaps they are
     both real and artefacts (i.e., the values are correct, but the poor spatial
     coverage in the 1860s means
     that they aren't really valid for the hemisphere as a whole)?
     And, there definitely seems to be a fairly abrupt change (decrease) from the
     1890s to 1900s in the US
     and elsewhere.
     Cheers
     Tim
