cc: Eystein Jansen <Eystein.Jansen@geo.uib.no>
date: Tue, 19 Jul 2005 15:36:06 -0600 (MDT)
from: Bette Otto-Bliesner <ottobli@ucar.edu>
subject: Re: [Wg1-ar4-ch06] Comments on exec bullets
to: Stefan Rahmstorf <rahmstorf@ozean-klima.de>

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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
______________________________________________

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