Saturday, June 9, 2012


date: Fri, 7 Jul 2006 12:44:43 -0600 (MDT)
subject: [Wg1-ar4-ch06] IPCC Figure 6.6 - Last Interglacial

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)
* 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)?,

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
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

--------------------- ---------------------
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


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