date: Mon, 10 Jul 2006 03:52:43 -0400
from: "W.R. Peltier" <peltier@atmosp.physics.utoronto.ca>
subject: Re: [Wg1-ar4-ch06] IPCC Figure 6.6 - Last Interglacial
to: ottobli@ucar.edu, wg1-ar4-ch06@joss.ucar.edu

Hi Bette,

      Of course the left panel should be kept as a multi-model 
average. It would appear to be the best way to emphasize commonality 
and thereby to minimize divergence.

Cheers
Dick






At 02:44 PM 07/07/2006, ottobli@ucar.edu wrote:
>Dear All,
>
>There are several issues to discuss and resolve concerning the last
>interglacial figure (6.6) in our chapter.
>
>Right panel: This panel shows the Greenland Ice Sheet (GIS) minimal extent
>and ice thickness for the last interglacial. It is an average of the
>minimal configurations of the GIS from three published results - Tarasov
>and Peltier (2003), Lhomme et al. (2005), and Otto-Bliesner et al. (2006).
>The colored dots represent an assessment of ice core observations on
>whether ice disappeared at these ice core sites during some point in the
>LIG, which I would like your views on:
>
>* White - Ice remained through LIG: N(NGRIP), S(Summit-GRIP and GISP2)
>R(Renland)
>* Black - Ice disappeared during some time in the LIG: A(Agassiz), De(Devon)
>* Gray - Status of LIG ice at these sites is unresolved: C(Camp Century)?,
>D(Dye3)?
>
>Any additional references that I should include in the figure legend would
>also be useful.
>
>Left panel: This panel shows the summer (JJA) surface temperature change
>from 2 proxy compilations and an average of 2 model simulations. The data
>represents proxy estimates of peak summer warmth. Susan wanted the model
>panel to be an average of results from more than one model. The two
>simulations available for this average are CCSM, 130ka minus
>present(1990), published in Otto-Bliesner et al. (2006); and ECHO-G, 125ka
>minus preindustrial, published in Kaspar et al. (2005) [except using the
>preindustrial simulation from the IPCC database rather than the
>preindustrial simulation used in Kaspar et al. because of a problem with
>snow buildup and very cold temperatures over Greenland in the Kaspar et
>al.
>preindustrial simulation]. We had rationalized at the time of the SOD that
>these two modeling group results are roughly comparable for computing
>Arctic summer surface temperature anomalies based on the following forcing
>effects:
>
>                    CCSM                          ECHO-G
>             ---------------------          ---------------------
>             130ka  1990      R.F.          125ka    PI      R.F.
>CO2         280     355     -1.27          270     280     -0.19
>CH4         600    1714     -0.53          630     700     -0.05
>N2O         Pres   Pres        0           260     265       ~0
>
>del Solar (incoming divided by 4 times 0.7)
>69N,MJJ                     +8.12                          +6.95
>69N,JJA                     +1.25                          +4.88
>
>I do not really like averaging these two modeling results although we can
>argue that this is somewhat justified based on the comparable GHG+Solar
>radiative forcings for Arctic May-Jun-Jul (but not so for Jun-Jul-Aug).
>Notice also the teardrop pattern of temperature anomalies in northern
>Greenland, which are a feature of the ECHO-G differences. The results from
>CCSM alone can be seen in the left panel of Figure TS-24 which is not yet
>the multi-model figure. Averaging the two models also makes answering
>comment 6-1060 problematic. Should we keep the left panel as a multi-model
>average?
>
>Bette
>
>
>
>
>
>
>
>
>
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