Wednesday, November 30, 2011


cc: myles <>, Tim Barnett <>, Phil Jones <>, David Karoly <>, Jesse Kenyon <>, Reto Knutti <>, Tom Knutson <>, Toru Nozawa <>, Doug Nychka <>, Claudia Tebaldi <>, Ben Santer <>, Richard Smith <>, Daithi Stone <>, "Stott, Peter" <>, Michael Wehner <>, Xuebin Zhang <>, francis <>, Hans von Storch <>, Thomas R Karl <>, "Bamzai, Anjuli" <>, Chris Miller <>
date: Thu, 26 Apr 2007 13:00:48 +0100
from: Nathan Gillett <>
subject: Re: 3 things, please reply by May 2
to: Gabi Hegerl <>

On Jerry Mehl's paper:
I agree with the points raised regarding the timing of the integrations.
For the high-res runs, the paper already suggests a start-date 'during
the latter half of the 20th century', so I think it's just a case of
putting a fixed date in the title (e.g. 1970) to clarify this.
Similarly, for the low-res runs, a pre-industrial spin-up and 20th
century run are already suggested, so again a start date in the title
(1900), is all that is required. From a practical point of view, these
continuous past to future simulations will be useful for doing
up-to-date detection - we'll be able to do attribution studies up to
2010 or 2012, or whenever, rather than only up to 8 eight years ago, as
is the case now. For impacts D&A, it will be useful to have non-climate
variables archived and publicly available as well e.g. carbon fluxes,
forest fire, land cover, ice sheet variables etc, where available. A
separate natural-only ensemble, run to ~2010 (assuming no future
volcanos and extrapolated solar forcing) would also be very useful for D&A.

From a policy and communications perspective I think it would be very
useful to have some emissions-driven integrations - a benchmark
business-as-usual, and one or more mitigation scenarios. These would
allow the community to answer the question 'Is it worth doing something
about climate change?', 'What are the costs of not acting to mitigate
climate change?', and would allow WGII and III to do cost-benefit
analyses of mitigation scenarios. Commenting on the AR4 one of the most
common questions which I'm asked is 'Is it too late act? - ie. what
climate change is going to happen anyway, and what can we hope to avoid
by changing policy?'. While I can see the benefits of the proposed
prescribed concentration stabilisation scenarios in terms of
intercomparing model climate responses and carbon cycles, I don't think
they will be as useful for answering these policy-relevant questions,
except in an indirect manner. To have only stabilisation runs assumes a
solution to the climate change problem without looking first at what
would happen if no action were taken. I appreciate this isn't really an
IDAG point, but would like to raise it anyway.

Any time in the proposed meeting window would be fine for me,



Minor points on the paper:
For S Hemisphere climate specifying ozone is important - SHem ocean
circulation and associated carbon flux changes, Antarctic temperature
change etc. Randel and Wu (2007) anomalies would be suitable in the
past, and either CCM output for the future, or depletion scaled by EESC.

I know it's only a schematic, but the temperature curve should look
different to the CO2 curve in Fig 1.

Gabi Hegerl wrote:
> Hi IDAG people,
> Three things:
> Jesse has put the collection of powerpoints from our meeting
> (those that people were not uncomfortable to
> share) on a webpage, instructions below, you are welcome to find talks and get them.
> Secondly, I attach Jerry Meehls writeup on the planned AR5 experiments, it would be
> helpful if we could comment on them as group. Please send comments to me, and I will
> collect and circulate our group reaction before sending to Jerry. My personal view is
> that the high-res near future runs are a great idea, but should start early enough for
> us to do some high res attribution, so eg 30-50 years over the 20th before going into
> 21rst.
> Also, Doug says that if we would soon decide on our next meeting timing, we may be able
> to get a particularly attractive location at NCAR (forgot what its called). We tentatively
> planned some 3 day window between February 8 to march 16. Myles points out that
> Brits wanting to bring kids would do well with dates on either side of the weekend
> 16-17 February for the Southern part, and 9-18 for the Northern part (which is when school
> is out).
> Greetings
> Gabi
> -------- Original Message --------
> Subject: sprng mtg presentations
> Date: Wed, 18 Apr 2007 14:36:51 -0400
> From: JKenyon <>
> To: Gabi Hegerl <>
> Dear colleagues,
> a collection of powerpoints from our Spring meeting is available as a
> download in a gzipped tar file.
> The file can be found at the top of our special web page for the spring
> meeting at:
> Please let me know if this form is unsuitable for you. We did this
> because there was some concern from members that they didn't want the
> presentation easily available, so instead of linking in each individual
> presentation, we thought it made it less attractive to casual surfers to
> zip it and tar it as one large file. Also note that the webpage itself
> is not linked to any other webpage - you have to type in the address
> directly.
> If you would also like a copy of Mike Wehner's presentations, please
> contact him directly.
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Jesse Kenyon
> Division of Earth and Ocean Sciences,
> Nicholas School for the Environment and Earth Sciences,
> Box 90227
> Duke University, Durham NC 27708
> Ph: 919-681-8160
> email:
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Gabriele Hegerl
> Division of Earth and Ocean Sciences,
> Nicholas School for the Environment and Earth Sciences,
> Box 90227
> Duke University, Durham NC 27708
> Ph: 919 684 6167, fax 684 5833
> email:,

Dr. Nathan Gillett,
Climatic Research Unit,
School of Environmental Sciences,
University of East Anglia,
Norwich NR4 7TJ, UK.
Tel: +44 (0) 1603 593 647
Fax: +44 (0) 1603 507 784



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