date: Tue, 09 Jan 2007 17:02:55 +0000
from: Brian Hoskins <b.j.hoskinsatXYZxyzding.ac.uk>
subject: Re: IPCC WG1 Observations Conference Call
to: Kevin Trenberth <trenbertatXYZxyzr.edu>
Most of the comments I just sent to you still apply. I do think more
slides need to be cut.
I like the new TC slide.
I am not very keen on including one temperature trend line which
corresponds to none of the periods we have in the Report. As an
alternative you could put the 25 year trend line on and say in your talk
that this line in fact fits the record quite well back to the late 60s.
I hope there will be a splash in the next polar bear version!
Kevin Trenberth wrote:
> Hi all
> Attached is a new version of the proposed ppt on obs. I have included
> a different version of the global mean temperature curve with just one
> trend line on it: see if you think the message related to that is the
> right one; and the one with all the trtend lines is hidden in reserve.
> I now have just 1 hurricane slide with 2 in reserve.
> I also had some fun with the last slide, following Susan's suggestion
> (that I am sure she did not intend me to follow up on). Make sure you
> play that with slide show turned on.
> Anyway the bottom line is that without the last slide there are now 22
> slides, and 8 and 9 essentially count as 1 (or leave 9 out), so it
> would be order 22 minutes. I could remove a slide like slide 20 but
> then I would have to take extra time on the previous slide to explain,
> and so I don't think much would be gained. Slide 18 would be short
> and acts as a segue to drought.
> Jurgen, should I add your slides to this? Do you want to change them,
> maybe to have a similar format, with a header that has the main
> message? Peter, do you also want me to add yours?
> Brian Hoskins wrote:
>> Dear All
>> I kept quiet over the discussion about trend lines as I think the
>> final result of not putting them on the 3 curves in the SPM is the
>> right one. However I certainly defend the use of the 25, 50,100, 150
>> year trend lines on the temperature curve as in the TS and Chapter 3
>> as being better than the alternatives. A linear fit may not be a good
>> one but when one is trying to make the smallest number of assumptions
>> it is more defensible than for example putting in seemingly arbitrary
>> break-points. The picture also gives a visual impression of how
>> representative the average rates of change numbers are.The fact that
>> the trend lines for different time-wondows are all different itself
>> shows that the linear fit is not good for the longer time-scales.
>> The monotonically increasing slopes as one moves from the longer to
>> the shorter time-scales is a strong indication of acceleration, but I
>> would not put this in the same sentence as the word "unequivocal".
>> Best wishes