from: Keith Briffa <k.briffaatXYZxyz.ac.uk>
subject: Re: Holocene paper
to: f055 <T.OsbornatXYZxyz.ac.uk>
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:
well, got here ok.
Not much to do today as Mike is lecturing and his post-doc is away (but only
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
We really need to get the review process going - I've told Mike that it is
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
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
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
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)
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