Wednesday, December 28, 2011


From: Gabi Hegerl <>
Subject: Re: comments on AR5 experimental design - reply by Aug 28 (thursday)
Date: Wed, 27 Aug 2008 09:33:33 +0100
Cc:, JKenyon <>, Myles Allen <>, 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 <>

Thanks Tim! We'll have another round later, confirmed by Tim, when we
discuss storage and
documentation - probably should try before WGCM meeting so that David
can present results.

the 'near term prediction' is a mip all by itself, so there will be some
guidance coming up hopefully!
In terms of ensemble size: for the stuff I was involved in, even one run
from a model was good since
it increased the overall ensemble size for multi model means and
estimates of variance - did you analyze
models individually? I would be keen to hear from the group:

is say a single 20th c run, single natural only run, single ghg run
a) useless
b) much better than nothing?

| vouch for b) for things I was involved in but it would be good to know
for which applications its a!

Tim Barnett wrote:
> 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.

Dr Gabriele Hegerl
School of GeoSciences
The University of Edinburgh
Grant Institute, The King's Buildings
West Mains Road
Phone: +44 (0) 131 6519092, FAX: +44 (0) 131 668 3184

The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.


No comments:

Post a Comment