cc: p.jones@uea.ac.uk, rbradley@geo.umass.edu
date: Mon, 08 May 2000 08:23:58 +0000
from: "Dr. Nanne Weber" <weber@knmi.nl>
subject: Re: papers
to: "Michael E. Mann" <mann@multiproxy.evsc.virginia.edu>

"Michael E. Mann" wrote:

> Hi Nanne,
>
> Thanks for your message. The Middle East paper is presently in final
> revision, and I'll be sure to send you a copy (or let you know when it is
> posted on the website) when the final version is ready.
>
> Regarding the European temperature trends, I wonder if we might be talking
> about slightly different things here?

Hi Mike,

>
>
> Just to doublecheck, I have confirmed from the East Anglia instrumental
> surface temperature data that the 20th century trends for the cold
> (Oct-Mar) and warm (Apr-Sep) seasons averaged over all of Europe are of the
> same sign (positive) and similar magnitude (roughly 0.5 and 0.3 C
> respectively). This is actually the primary feature in the plot that I
> showed which was similar (the warming trend of the 20th century) in both
> seasons. And that is from the instrumental record itself, and cannot be in
> dispute.
>
> The lower mean value of both warm and cold-season temperatures in Europe
> during the pre-20th century interval is also clearly evident in the
> instrumental record alone. However, the trends during the 18th and 19th
> century are different, and perhaps this is what you are talking about.

Yes, this is what I meant. The trend for the period 1750-1900 is a cooling
for summer and a warming for winter. (We did look at three-month mean
seasonal values, so this might make the difference more pronounced
than when you look at 6-month mean seasonal values.) I thought that you
were talking about the trend over the
whole available period, when you showed the plot at the EGS. The trends for
the 20th century are the same in summer and winter.

> Our
> reconstructions do not suggest otherwise.

OK
This (the different seasonal trends) is the interesting point really.
It suggests internal climatic
variability as an important factor, rather than external forcing.
At least for the regional, seasonal records. In the case of external
forcing, you would expect the signal to persist throughout the year.


>
>
> Our seasonal reconstructions for the European gridpoints resolve roughly
> 25-30% of the variance (using the long available European surface
> temperature records back through the 18th century) in long-term
> cross-validation for both warm and cold season independently, so the long
> available instrumental surface temeprature data series confirm, rather than
> contradict, our reconstructions.
>
> Perhaps there is a significant difference in the 3 month seasonal means you
> are looking at and the somewhat broader 6 month seasonal means that we use?
> In any case, I'm am quite confident that the available instrumental
> information validates our European seasonal reconstructions back through
> the 18th century.
>
> I've cc'd this message to some other individuals (Phil Jones and Ray
> Bradley) who have looked at the long instrumental European data in detail,
> and might be able to comment further...
>
> mike
>
>

Best wishes,
and sorry for the confusion,

Nanne