Saturday, May 19, 2012


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date: Tue, 6 Apr 2004 12:45:29 +0100
from: "McMahon, Michael (HSE)" <mcmahomatXYZxyzcom>
subject: RE: Tyndall/CMI Symposium Summary
to: <>, "John Shepherd" <>


I too would prefer to avoid suggesting that there is an optimum concentration of CO2. The aim of the UNFCCC is to limit concentration at at level that would avoid serious damage...etc. Increased crop yields may be a "positive" side effect.

I am a little concerned about the frequency of use of the word "likely" when we are talking about a future that is very uncertain.

For instance, nuclear power; can we just say that nuclear power is one of the options. In fact could it be better to include nuclear in the "mainstream" options in the previous sentence under zero (low) carbon energy sources.

Again the use of the word "likely" in the third bullet point is almost suggesting that macro-engineering approaches will be inevitable. It is up to policy makers and elected decision makers to determine whether "conventional methods" will be sufficient to meet the stated goal.

The macro-engineering options need further R&D support to ensure that we have the option of implementing them in the future; we must be careful not to position them as a reason for not making the tough decisions that need to be made now to get us on a path to stabilisation.

Another example is shown below - can we really say this - what we should be asking for is R&D funding to do the analysis to determine the levels of risk or at least the comparative levels of risk. (ie the next bullet)

""""* Based on currently available scientific knowledge, it appears likely that it would be less
risky to endure doubled (or higher) CO2 concentrations, together with a small reduction in
insolation, than to do so without such a reduction.""""

Finally, in order to provide some context for the interested, but not expert, reader, would it be possible to provide an introductory or context paragraph decribing what we mean by macro-engineering options.

Thanks for the opportunity to comment.

Best regards,

Mike McMahon
Senior Advisor Climate Change

-----Original Message-----
From: Lee R. Kump []
Sent: 05 April 2004 15:57
To: John Shepherd
McMahon, Michael (HSE);;;;;;;;;;;;; V
Subject: Re: Tyndall/CMI Symposium Summary

Hi John and other colleagues,

I support the document as it stands, but suggest the following minor

a) Concerning the bulleted point on the bottom of the first page about CO2
reductions: I recommend that this read:

"Substantial reductions of present and future CO2 emissions, or mitigation
of these
emissions through CO2 capture, are therefore likely to be needed . . ."

for consistency with the rest of the document.

b) I do not share the opinion expressed in the next bullet that we can
assume that
there is an "optimum" CO2 level other than that to which society has
adjusted over the
previous millennia (280ppmv). Crops may grow better under elevated CO2 all
other factors being
the same, but we cannot guarantee the latter even with albedo modification
and Ken's modeling, especially at the regional level. Might we set this
statement and others
for which there may not be consensus aside or into their own section? Or
perhaps it could
appear in the final section, and begin with "Some participants feel that
these adverse . . ."

c) in the following section, in mentioning diffuse sources you
paranthetially state "(transport)"
which may be ambiguous (confused with, e.g., atmospheric transport of the
gas). How about
replacing it here, and the couple places it appears below, with



John Shepherd said:
> Dear colleague
> Herewith at long last a revised version of the Symposium Summary
> document, both as a change tracked Word Document, and a "clean" pdf. I
> have
> (I hope) included in some way all the excellent suggestions received
> (thank
> you all for these), usually in a slightly edited form, including a couple
> which may be controversial (e.g. those from Jim Lovelock & David Keith). I
> did not deliberately suppress any, so if yours has gone missing please let
> me know.
> I think this now needs another careful look in the cold light of day, if
> you would be able to do that please...
> We have started constructing the web-site too, and hope to have this all
> up and accessible in a few weeks time, so fairly early comments would be
> appreciated (although I am actually away all next week anyway)
> With best wishes
> John

Lee R. Kump
Dept. of Geosciences
Penn State
535 Deike Bldg.
University Park, PA 16802
+1 (814) 863-1274 (phone)
+1 (814) 863-7823 (fax)

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