date: Wed, 18 Oct 2000 20:06:18 +0300
from: Timothy Carter <REDACTED
subject: Re: THC Europe
Martin et al.,
Some responses [TC],
At 12:38 18/10/REDACTED
>Tim, Mike, Zbyszek:
>Following Mike's and Tim's comments, I think I am now back where I started
>which was to be able to state that it is the IPCC position (since you two
>the scenario 'people' for WGII) that a) there are no scenarios for impacts
>possible THC change, b)no assessment has been done AND c) THEREFORE THE IPPC
>HAS CONCLUDED NO ASSESSMENT CAN BE MADE OF IT AT THIS POINT.
[TC] IPCC doesn't make conclusions of this kind - we, the assessors, in our
chapters draw the conclusion. You are the IPCC Martin, didn't you realise
>I am very happy if that is the position (which I think waswhere we
>years ago). I may have misunderstood Tim'spoint that the Polar ch and ch 19
>deal with THC change (but if it is to say no more than the para above, then
>we are all agreed).
[TC] I didn't intend to mislead. I only pointed out where the issue has
been raised. Chapter 19 engages in some detailed speculation on the issue
(did you read their sections?), but without any examples of impact studies
to draw on.
>Regarding the phrase 'IPCC position'? Would it be wise to check that
>McCarthy /Watson have the same understanding as we do.
[TC] You could try, but it has been tricky getting anyone to make
statements about anything. It seems that a few people have a very strong
say, and no matter how much talking goes on beforehand, the big decisions
are made at the eleventh hour by a select core group.
For example, currently the WG I extremes Table has been completely
(radically!) revised by WG I for their SPM, and I will now have to do the
same to our WG II Table for consistency. The THC entries in the Table are
anyway unique to WG II, because WG I did not tabulate this extreme.
Indeed, only a small part of the discussion in WG I has been about the THC,
and the only prominent statement that is made in the SPM (as I understand
it) is from Ch 9 - that the THC is expected to weaken. THC collapse and the
cooling implications for Europe is not considered explicitly - it is buried
in the chapter 7 text.
So maybe that answers your question - it is not considered likely enough
and/or there isn't enough scientific evidence to merit a headline statement
You might like to find out the Chapter 19 view on this. That is the chapter
in which this issue is pursued most vigorously. John Schellnhuber and
Barrie Pittock have taken the lead on this.
>The reason I would like to clarify this is the following: a) It is certain
>that readers of TAR will ask: What will be would be the effect of possible
>change in THC on Europe? Our answer would be that IPCC has not assessed
>(because scenarios have not been developed nor impact assessments done).
>riposte may be: Then why not, but that is a riposte to the IPCC not us ; b)
>on the other hand, Mike, Jorgen and I will be presenting the ACACIA results
>to a press riefing on 1st November; and the same Q may well arise and we
>would then give the same response (since ACACIA is a an IPCC precursor).
[TC] I suppose so. The IMAGE exercise (hardly a study) is the only one I
know of, and that used an arbitrary scenario and was almost 10 years ago!
I think we would have to say that no AOGCMs show an abrupt collapse, and so
scenarios have not be constructed or impact studies conducted to consider
this unlikely phenomenon.
>I think I am now clear about this, but I would like to be clearer about how
>far this is an IPCC position.
Dr. Timothy Carter
Finnish Environment Institute
Box 140, Kes