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. Tim >Date: Tue, 31 May 2005 19:49:16 +0200 >From: Jesus Fidel Gonzalez Rouco >Subject: Re: ECHO-G solar forcing >To: Tim Osborn >X-Accept-Language: en-us, en >User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030624 > Netscape/7.1 >X-Spam-Score: 0.6 >X-Spam-Level: / >X-Spam-Flag: NO > >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: >http://chubasco.fis.ucm.es/~fi/for_wpa01/for_wpa01.html > >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 :-( >greetings >Fidel > >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 >> >>Tim >>Dr Timothy J Osborn >>Climatic Research Unit >>School of Environmental Sciences, University of East Anglia >>Norwich NR4 7TJ, UK >> >>e-mail: t.osborn@uea.ac.uk >>phone: +44 1603 592089 >>fax: +44 1603 507784 >>web: http://www.cru.uea.ac.uk/~timo/ >>sunclock: >>http://www.cru.uea.ac.uk/~timo/sunclock.htm > > >-- >Dpto. Astrofisica y CC. de la Atmosfera >Facultad CC Fisicas, Universidad Complutense de Madrid >28040 Madrid, Spain. Tel(fax): +34 91394 4468 (4635) >http://chubasco.fis.ucm.es/~fi/ Dr Timothy J Osborn Climatic Research Unit School of Environmental Sciences, University of East Anglia Norwich NR4 7TJ, UK e-mail: t.osborn@uea.ac.uk phone: +44 1603 592089 fax: +44 1603 507784 web: http://www.cru.uea.ac.uk/~timo/ sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm