cc: joos <joos@climate.unibe.ch>, Eystein Jansen <eystein.jansen@geo.uib.no>, Bette Otto-Bleisner <ottobli@ncar.ucar.edu>, cddhr@giss.nasa.gov
date: Fri Sep  1 15:45:38 2006
from: Keith Briffa <k.briffa@uea.ac.uk>
subject: Re: urgent IPCC need
to: Stefan Rahmstorf <rahmstorf@ozean-klima.de>, Jonathan Overpeck <jto@u.arizona.edu>

   I forgot to say that I too disagree with removing the first sentence re simulations being
   consistent with reconstructed NH temps. As Sefan says we need the context , and our results
   are independent of Chapter 9 in this regard.
   Keith
   At 15:37 01/09/2006, Stefan Rahmstorf wrote:

     Hi Peck,
     Martin as in Manning? I have found his feedback very useful so far, so we should
     definitely look at what he suggests - he mostly tends to look for whether our sentences
     are clear. Obviously, he cannot suggest real changes in meaning, only issues of clarity,
     but the latter I would take very seriously. Mostly I find his small rewordings good, I
     comment on the larger points and exceptions below.
     - I am against deleting the bullet on speed of deglacial change. This point is extremely
     effective. Just two days ago an oil industry person told me that there have been big
     natural climate changes like ice ages in the past, hence we need not worry. I responded
     that the biggest warming in recent climate history was the end of the last Ice Age - but
     that warming by about 5 C took about 5,000 years, not a hundred. "Oh" he said, "Really
     so long? I didn't know that." I think it is a very important point, we need to make it.
     Maybe not in term of "average rate", may we should just say: the warming of 4-7 C took
     about 5,000 years, as compared to a future change of up to the same magnitude within a
     century.
     - Next ice age bullet in 30k seems fine to me.
     - exceptional warmth: the SPM said:
     20th C T increase likely the largest in a millennium - that is strengthened (perhaps
     very likely now?)
     1990s likely the warmest decade in a millennium - that again is strengthened
     1998 likely the warmest year - I'd say this is unchanged (except for 2005 challenging
     it), likely is only 66%! Even though the annual proxy data may be uncertain, as a
     physicist I would find it unlikely that there is a mechanism to cause a big warm outlier
     year that beats 1998 from a much cooler background state. How would that work - where
     would the heat come from?
     So in my view we could actually say that these past SPM statements held up or were
     strengthened - but in fact I also like the bullet as it is.
     - [DEL: Paleoclimate model simulations are broadly consistent with the reconstructed NH
     temperatures over the past 1000 years. :DEL] The rise in surface temperatures since 1950
     very likely cannot be reproduced without including anthropogenic greenhouse gases in the
     model forcings, and it is very unlikely that this warming was merely a recovery from the
     pre-20^th century cold period.
     On this I disagree with deleting the first sentence, as the second one needs it to
     follow logically. And why should the paleo chapter suddenly make a statement on
     post-1950 warming, if it is not in the context of the past millennium?
     Cheers, Stefan
--
To reach me directly please use: [1]rahmstorf@ozean-klima.de
(My former addresses @pik-potsdam.de are read by my assistant Brigitta.)

Stefan Rahmstorf
[2]www.ozean-klima.de
[3]www.realclimate.org

   --
   Professor Keith Briffa,
   Climatic Research Unit
   University of East Anglia
   Norwich, NR4 7TJ, U.K.

   Phone: +44-1603-593909
   Fax: +44-1603-507784
   [4]http://www.cru.uea.ac.uk/cru/people/briffa/

