date: Wed Jun 15 15:54:12 2005
from: Keith Briffa <k.briffa@uea.ac.uk>
subject: Fwd: Re: [Wg1-ar4-ch06] comments to 6.3.2.1 (mainly for Keith)
to: Tim Osborn <t.osborn@uea.ac.uk>

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     Date: Mon, 10 Jan 2005 18:01:42 +0100
     To: Keith Briffa <k.briffa@uea.ac.uk>, David Rind <drind@giss.nasa.gov>,
      wg1-ar4-ch06@joss.ucar.edu
     From: Eystein Jansen <eystein.jansen@geo.uib.no>
     Subject: Re: [Wg1-ar4-ch06] comments to 6.3.2.1 (mainly for Keith)
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     Hi,
     interesting discussion on an important topic. If space is the limiting factor we may
     have to evaluate whether to cut back on less central issues elswhere in the chapter. We
     will to a large extent be judged on how we tackle the hockey stick, sensitivity,
     unprecedented 20th century warming isuues in view of palaeo, and if a slight expansion
     is what it takes to do this properly, then I  am sympathetic to that (without having
     heard Peck on the issue).
     Cheers,
     Eystein
     At 16:32 +0000 10-01-05, Keith Briffa wrote:

     thanks David
     have to say that it is very difficult to say much in the minimal space - and we really
     need a page to discuss the problems in the reconstruction and and interpretation of the
     various forcings in different models - I am just going to put this down in an over
     abbreviated way and ask for specific corrections for you and Stefan et al. The detail
     perhaps depends on what the final Figure looks like and Tim is trying to put it together
     but lots of weird and interesting stuff / questions arise as we do - especially relating
     to past estimates of solar irradiance used by different people. At 15:29 10/01/2005,
     David Rind wrote:

     (I tried to send this earlier and it got hung up; apologies if it eventually gets
     through and you get a second version.)
     Well, yes and no. If the mismatch between suggested forcing, model sensitivity, and
     suggested response for the LIA suggests the forcing is overestimated (in particular the
     solar forcing), then it makes an earlier warm period less likely, with little
     implication for future warming. If it suggests climate sensitivity is really much lower,
     then it says nothing about the earlier warm period (could still have been driven by
     solar forcing), but suggests future warming is overestimated. If however it implies the
     reconstructions are underestimating past climate changes, then it suggests the earlier
     warm period may well have been warmer than indicated (driven by variability, if nothing
     else) while suggesting future climate changes will be large.
     This is the essence of the problem.
     David
     At 9:28 AM +0000 1/10/05, Keith Briffa wrote:

     THanks Stefan
     At 21:13 07/01/2005, Stefan Rahmstorf wrote:

     Keith,
     some comments added in the text for the past millennium, plus I wrote some extra
     sentences on the implications of the dispute (repeated below).
     Hope it is useful,
     Stefan

     Note that the major differences between the proxy reconstructions and between the model
     simulations for the past millennium occur for the cool periods in the 17th-19th
     Centuries; none of these reconstructions or models suggests that there was a warmer
     period than the late 20th Century in the record.
     A larger amplitude of preindustrial natural climate variability does not imply a smaller
     anthropogenic contribution to 20th Century warming (which is estimated from 20th Century
     data, see Chapter XXX on attribution), nor does it imply a smaller sensitivity of
     climate to CO2, or a lesser projected warming for the future.

     --
     Stefan Rahmstorf
     <[2]http://www.ozean-klima.de>[3]www.ozean-klima.de
     [4]www.realclimate.org
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     --
     Professor Keith Briffa,
     Climatic Research Unit
     University of East Anglia
     Norwich, NR4 7TJ, U.K.
     Phone: +44-1603-593909
     Fax: +44-1603-507784
     [6]http://www.cru.uea.ac.uk/cru/people/briffa/
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     --
     Professor Keith Briffa,
     Climatic Research Unit
     University of East Anglia
     Norwich, NR4 7TJ, U.K.
     Phone: +44-1603-593909
     Fax: +44-1603-507784
     [9]http://www.cru.uea.ac.uk/cru/people/briffa/
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     --
     ______________________________________________________________
     Eystein Jansen
     Professor/Director
     Bjerknes Centre for Climate Research and
     Dep. of Earth Science, Univ. of Bergen
     Allgaten 55
     N-5007 Bergen
     NORWAY
     e-mail: eystein.jansen@geo.uib.no
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     -----------------------
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   --
   Professor Keith Briffa,
   Climatic Research Unit
   University of East Anglia
   Norwich, NR4 7TJ, U.K.

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

