date: Fri, 7 Jul 2006 12:44:43 -0600 (MDT) from: ottobli@ucar.edu subject: [Wg1-ar4-ch06] IPCC Figure 6.6 - Last Interglacial to: wg1-ar4-ch06@joss.ucar.edu 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 _______________________________________________ Wg1-ar4-ch06 mailing list Wg1-ar4-ch06@joss.ucar.edu http://lists.joss.ucar.edu/mailman/listinfo/wg1-ar4-ch06