Thursday, May 3, 2012

3763.txt

cc: "jason.lowe@metoffice.com" <jason.loweatXYZxyzoffice.com>
date: Thu Apr 30 15:25:32 2009
from: Tim Osborn <t.osbornatXYZxyz.ac.uk>
subject: Re: Query with thermal expansion / temperature input data
to: "Brown S." <sb20atXYZxyzon.ac.uk>, Nigel Arnell <n.w.arnellatXYZxyzding.ac.uk>

Hi Sally,
The data came from Malte Meinhausen by way of Sarah Raper. An alternative answer to that
question is that the data came from the AR4-version of MAGICC 4.2.
As I indicated earlier to Nigel, my understanding is that MAGICC (AR4-version) typically
overestimated thermal expansion compared with GCMs, which is one of the reasons why MAGICC
sea level rise wasn't used in AR4. Appendix 10.A of AR4 WG1 discusses this.
I believe there is a post-AR4 version of MAGICC which does a better job with thermal
expansion; I/we could ask Malte Meinhausen or Sarah Raper if we can have the thermal
expansion from that version.
Re. CO2. Is this the line that you are asking about:
"CARBON CYCLE FEEDBACK SETTING: default (1)"
As far as I know, the "default" strength of the carbon cycle feedback is not zero strength
(i.e. CO2 feedback turned off), but rather is the "standard" CO2 feedback strength as
described in Fig. 10.29 of AR4 WG1. That is certainly how it was explained to me before,
but I will check this with Sarah Raper to make sure.
Hope that helps,
Tim
At 13:54 30/04/2009, Brown S. wrote:

Hello,
We are finalising the sea-level scenarios and have checked the output data with Jason
Lowe, who has some queries.
Thermal expansion values (in particular) are higher than Table 10.7 (p820 WG1 IPCC
2007), and also temperature seems a bit higher. Where did the data come from? Jason
wanted to check about the CO2 concentration - was this turned on during the runs (just
says the default setting is 1 - see accompanying file as an example)? How does this
follow with p5 of the Experimental Design Note (I have V5.1) which says 'The project
therefore scales each climate model pattern by global temperatures estimated with its
own set of tuned MAGICC4.2 parameters, assuming a medium carbon cycle feedback and a
default radiative forcing for doubled CO2 concentration of 3.7 W/m2.'?
Sally
-----------------
Sally Brown
School of Civil Engineering and the Environment
University of Southampton
02380 592883 (new telephone number)

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