Monday, June 11, 2012


cc: "JKenyon" <>, "Myles Allen" <>, "Tim Barnett" <>, "Nathan" <>, "Phil Jones" <>, "David Karoly" <>, "Knutti Reto" <>, "Toru Nozawa" <>, "Tom Knutson" <>, "Doug Nychka" <>, "Claudia Tebaldi" <>, "Ben Santer" <>, "Richard Smith" <>, "Daithi Stone" <>, "Stott, Peter" <>, "Michael Wehner" <>, "Francis Zwiers" <>, "Hans von Storch" <>
date: Tue, 26 Aug 2008 16:47:25 -0700 (PDT)
from: "Tim Barnett" <>
subject: Re: comments on AR5 experimental design - reply by Aug 28
to: "Gabi Hegerl" <>,

hi real haste.....people will use the AR5 data set for impact
studies no doubt about it. so what will they find when they jump
in....same as we did trying to do the western D&A work with AR4....a very
disparate set of numbers.
1.some models don't give the data one would like.
2.some models have only 1 realization...which makes them useless. we
found that with multiple realizations one can do statistics with ensemble
techniques which give a lot more statistical power. suggesting 10 member
ensembles. with less the S/N can be small...e.g. we could not use the
GFDL runs very well as they were so noisey and had few (5) realizations)
3. daily data is required. storage is cheap these days so at least daily
data for order 100 years is desired. otherwise it is finageled a la the
current downscaling methods (save one).
4. the 20th century runs need to go to 2015 as suggested by IDAG. we had
to stop at 1999 and lost 8 years we would well like to have studies.
5. some of the variables we needed to compare with satellite obs were
largely missing, e.g. clouds information.
6. to Mike's point....just what data is going to be saved?
7. i hope potential users of the data aside from the modeling groups get
a say in what is archived. we are to the point now where policy makers
want our best guesses as to what will happen in the next 20 years. the
people who will make those 'guesses' are most likely not in the major
model centers.

I invite David Pierce to chip in here as he spend alot of time in the
details of the data sets and associated problems.

sorry to be so hasty but such is life at the moment. best, tim

> Hi IDAG'ies,
> As you probably know, a proposal for the AR5 experiments is being
> circulated in the moment, with comments due by September 1. This will
> then be presented at the working group for coupled modelling (WGCM)
> meeting in Paris, which David Karoly will attend.
> Peter Stott and I discussed the draft when I visited last week, and we
> drafted a response and suggestions from IDAG (attached) Please let me
> know if you are ok with this (if I dont hear back I assume you are),
> if you suggest changes and if you want us to add another topic/concern.
> I would need this by next thursday to add it to a comment 'from IDAG'
> to be sent in time, and then hopefully David can present this also in
> Paris at the WGCM meeting.
> hope you all had a nice summer, and still remember our next meeting in
> planning, and your IDAG tasks :))
> Gabi
> p.s. we were wondering also about forcing, and if the forcing issue
> (how stored, synchronized?) should be added. However, given even some
> 'rich' modelling groups worry about getting the mandatory experiments
> through we should however not hope that groups will run more than 1
> single forcing set for the 20th century, and arguments against
> synchronizing are that its not feasible for many forcings (eg
> aerosols) and that we loose quite a bit of information if only a
> single, for example, set of solar forcings were used and with this
> open the AR5 up for criticism. Ideally, of course, one center would
> systematically explore all the forcings - but I am not sure somebody
> is planning to do this - in that case, a common set of 20th century
> forcings may be an advantage. Based on some EU project, forcings are
> synchronized for some European modeling centers - we could draw
> attention to that if you feel strongly about this...anyway, I hesitate
> to start a discussion about this...
> --
> Gabriele Hegerl
> School of GeoSciences
> University of Edinburgh
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.

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