cc: mmanning@al.noaa.gov, wg1-ar4-ch06@joss.ucar.edu, Marquis@ucar.edu, v.ramaswamy@noaa.gov, Valerie.Masson@cea.fr, p.m.forster@reading.ac.uk
date: Thu, 09 Feb 2006 15:44:34 +0100
from: Renato Spahni <spahni@climate.unibe.ch>
subject: Re: [Wg1-ar4-ch06] [Fwd: Greenhouse Gas Figure for IPCC]
to: Jonathan Overpeck <jto@u.arizona.edu>

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Dear all,

Thank you very much for including me as a contributer to this important 
report. I changed the EPICA/VOSTOK (CO2 also from Taylor Dome) figure 
accordingly:

- figure with N2O and antropogenic increase
- no shaded areas before MIS 11
- isotopes are shown as step plot with highest resolution published ( 
0-390kyr: EPICA Community Memebers, 2004; 390-650kyr: Siegenthaler et 
al. 2005, Spahni et al. 2005)
- for visibility reasons the line widths are smaller now
- the delta D label has probably a font problem, I converted it as a pdf 
this time

Let me know if I can be of further assistance.

All the best,
Renato


Jonathan Overpeck wrote:

> Hi Valerie et al. - let's all weigh in before Renato generates the 
> final SOD graphic. My thoughts
>
> 1) I don't feel strongly about the delta D data being smoothed or not 
> (it makes sense, but will it make a difference? - go ahead if others 
> agree), but I think we should keep isotopic data, rather than 
> temperature - to avoid the confusion with the most recent data not 
> being the warmest - or even close. It's regional temp, I know, but 
> some readers might realize this. We can say in the caption that delta 
> D is a regional temp record. I'm just one vote, here...
>
> 2) I agree with the vert grey shaded areas, and will go one step 
> farther for a compromise. I vote we keep the shading on the real 
> interglacials of the last 450kyrs, and delete the grey shading on the 
> earlier "interglacials" - they are different, clearly, and we can make 
> that point in the caption. Valerie's reasoning then works the other 
> way - the grey shading helps readers get the point about how the 
> length of interglacials comparable to the Holocene have varied, with 
> MIS 11 being the phattest.
>
> Thanks, Peck
>
>> Jonathan Overpeck a crit :
>>
>>> Hi Fortunat, Renato and friends: Here's my thoughts on what you have 
>>> sent wrt to chap 6:
>>>
>>> 1) for the EPICA/VOSTOK figure, I agree we should go with the 
>>> version WITH N2O and WITH the anthropogenic increase 
>>> (ipcc_ghg650kyr_v1ant) Renato - would you please resend with the 
>>> delta D label fixed. Thanks - otherwise, nice job.
>>>
>>>
>> I have a few comments on the figure ipcc_ghg650kyr_v1ant.
>>
>> - the deuterium data should be smoothed to appear with a resolution 
>> similar to the GHG records (we usually use step functions for 
>> deuterium plots because the measurements are conducted as averages 
>> for bag samples => not single points).
>>
>> - it is possible to show temperature fluctuations rather than 
>> deuterium, if you prefer.
>>
>> - I am worried about the vertical grey lines on this figure, assumed 
>> to define "interglacial periods". It is tricky and depends on some 
>> hypothesis (thresholds on deuterium or GHG). For instance stage 7.5, 
>> 7.3 should also appear as interglacials with the thresholds used for 
>> the other warm periods.
>> As we are aware of (preliminar) Dome C age scale problems for stages 
>> 13-15, the grey bars may give false impressions regarding the 
>> duration of the oldest warm episodes.
>>
>> Valrie.
>
>
>

-- 
______________________________

Renato Spahni

Climate and Environmental Physics
Physics Institute, University of Bern
Sidlerstrasse 5		
CH-3012 Bern, Switzerland

Phone: ++41 (0)31 631 44 76
Fax:    ++41 (0)31 631 87 42
spahni@climate.unibe.ch
www.climate.unibe.ch/~spahni
______________________________


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