Wednesday, May 23, 2012


date: Wed, 01 Jun 2005 12:29:15 +0100
from: Tim Osborn <>
subject: Fwd: Re: ECHO-G solar forcing
to: "Keith Briffa" <>

Here's the response to my query about whether they'd got the solar forcing
wrong in ECHO-G. It seems they're happy they got it right.


>Date: Tue, 31 May 2005 19:49:16 +0200
>From: Jesus Fidel Gonzalez Rouco <>
>Subject: Re: ECHO-G solar forcing
>To: Tim Osborn <>
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>Dear Tim,
>dont worry I understand your motivation.
>It is correct that the solar forcing is rescaled to the variance of Lean
>et al. There was only one factor applied to the Crowley data and that was
>the scaling for the Lean et al.
>The curve that was selected for that was the BE10/lean splice in Fig2 from
>Crowley 2000.
>As you indicate, the solar irradiance is the input to the model which
>reads solar constant values each year, not forcing. The values that are
>used to force the model are those in
>my web page for the model:
>you can have a look at any of the forced integrations. For innstance:
>Forced run: Erik1 (a01)
>Those plots specify actually the exact values that go into the model.
>Hope this is of help? let me know if you need more info. You can also
>discuss it with Edu, who actually prepared the forcings... of course I
>will be glad to
>provide you with any info that might be of help
>Sad about rumorology :-(
>Tim Osborn wrote:
>>Dear Fidel,
>>Keith Briffa, with some input from me, is preparing a section on the
>>climate of the last 2000 years for the next draft of the IPCC
>>Paleoclimate chapter.
>>We are including some model simulations and forcings from experiments of
>>the last 1000 years, and would like to include the ECHO-G Erik run.
>>We are concerned that some colleagues that we have met at various
>>meetings have the impression (possibly from Mike Mann?) that you did the
>>solar forcing "wrong" in this simulation - with variations that are
>>unrealistically strong.
>>I already know from the supplementary information in von Storch et al.
>>(2004) that you scaled the Crowley (2000) solar irradiance history to
>>have the same variance as the Lean et al. history, but the "rumours" talk
>>about much bigger differences than simply this rescaling. Some have
>>suggested that the conversion from solar irradiance to forcing [
>>*0.25*(1-albedo) ] was forgotten.
>>Knowing a little about running GCMs, I don't think this can be true
>>because I think you don't put this in as a radiative forcing, but instead
>>just vary the solar "constant" - then there is no conversion from
>>irradiance to forcing, and it can't be forgotten!
>>But Keith has asked me to double check with you anyway!
>>The attached file is an early draft of the figure, including panel (b)
>>showing the solar forcing (converted to a forcing by *0.25*(1-albedo),
>>and then smoothed with a 30 year filter).
>>It shows very little difference between ECHO-G forcing and the
>>others. Does this figure look right to you?
>>Many thanks in advance for your checking - and sorry to question your
>>capability (I just was asked to check)!
>>Best wishes
>>Dr Timothy J Osborn
>>Climatic Research Unit
>>School of Environmental Sciences, University of East Anglia
>>Norwich NR4 7TJ, UK
>>e-mail: <>
>>phone: +44 1603 592089
>>fax: +44 1603 507784
>>web: <>
>Dpto. Astrofisica y CC. de la Atmosfera
>Facultad CC Fisicas, Universidad Complutense de Madrid
>28040 Madrid, Spain. Tel(fax): +34 91394 4468 (4635)

Dr Timothy J Osborn
Climatic Research Unit
School of Environmental Sciences, University of East Anglia
Norwich NR4 7TJ, UK

phone: +44 1603 592089
fax: +44 1603 507784


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