cc: Eystein Jansen date: Tue, 19 Jul 2005 15:36:06 -0600 (MDT) from: Bette Otto-Bliesner subject: Re: [Wg1-ar4-ch06] Comments on exec bullets to: Stefan Rahmstorf 5. I think we need to provide the temperature range for LGM PMIP-2 simulations, because they all use the same boundary conditions and forcings and provide another measure of climate sensitivity for the models in Chapters 8 and 10. The response, globally and regionally, for LGM is quite dependent on the boundary conditions and forcings used. PMIP-2 simulations with dynamic vegetation are not yet available and changes to atmospheric aerosols are not included. Both forcings could result in some additional cooling, especially regionally, but also globally as you point out. Crucifix et al. using the slab version of HadCM3 (and not using PMIP-2 specifications) put the global-average contribution of vegetation changes at 0.6C, but they did not use the PMIP-2 specifications. Yes, Kim et al. did get 10C cooling in their LGM simulation but they did not include vegetation or aerosols changes so we cannot attribute their large cooling to full glacial cooling. Their run is truly an outlier for the forcings they did apply; they did not submit a new LGM simulation for PMIP-2. I suggest we reword into two bullets to clarify as follows: * The Last Glacial Maximum featured reduced atmospheric concentrations of greenhouse gases, increased atmospheric aerosols, and altered land ice and vegetation. In a coordinated international multi-model experiment (PMIP-2), models simulate a change in global mean surface air temperature change between the Last Glacial Maximum and the current interglacial of 3.1 to 5.1C when considering greenhouse forcing and continental ice changes (radiative forcing change of -4 to 7 W m-2). For full glacial conditions, models simulate even greater cooling of XXC. * Global cooling at the Last Glacial Maximum is comparable in magnitude with the projected global mean warming over the 21st century, although the warming after the Last Glacial Maximum happened over thousands of years rather than the 100 years expected in the future. 9. A paper submitted by the CAPE LIG members finds summer temperature anomalies 5C above present over most Arctic lands for the Eemian. Arctic warming of 6-8C at the end of this century is on the high end for the IPCCAR4 models. Chapman and Walsh's paper on the IPCC AR4 web site link for the Honolulu meeting gives projected temperature changes for 60-90 N of 1-5.5C for SRESB1, 2.5-7C for SRESA1B, and 4-9C for SRESA2 by the end of the 21st century. The 14-GCM mean map for the middle of the road SRESA1B gives cooling of 3-6C for 2070-2089. Bette ______________________________________________ Bette L. Otto-Bliesner Climate Change Research National Center for Atmospheric Research 1850 Table Mesa Drive / P.O. Box 3000 Boulder, Colorado 80307 Phone: 303-497-1723 Fax: 303-497-1348 Email: ottobli@ncar.ucar.edu ______________________________________________ _______________________________________________ Wg1-ar4-ch06 mailing list Wg1-ar4-ch06@joss.ucar.edu http://www.joss.ucar.edu/mailman/listinfo/wg1-ar4-ch06