HR: 10:50h
AN: PP52A-03 INVITED     [Abstracts]
TI: Climate Sensitivity of the Last Glacial Maximum from Paleoclimate Simulations and Observations
AU: * Otto-Bliesner, B L
EM: ottobli@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305 United States
AU: Brady, E
EM: brady@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305 United States
AU: Kothavala, Z
EM: zav@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305 United States
AB: Global coupled climate models run for future scenarios of increasing atmospheric CO2 give a range of response of the global average surface temperature. Regional responses, including the North Atlantic overturning circulation and tropical Pacific ENSO, also vary significantly among models. The second phase of the Paleoclimate Modeling Intercomparison Project (PMIP 2) is coordinating simulations and data syntheses for the Last Glacial Maximum (21,000 years before present) to allow another assessment of climate sensitivity. Atmospheric CO2 concentrations at the Last Glacial Maximum (LGM) have been estimated using measurements from ice cores to be 185 ppmv, approximately 50% of present-day values. Global, annual mean surface temperature simulated by the slab ocean version of the National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM3) shows a cooling of -2.8øC for LGM CO2 levels and a warming of 2.5øC for a doubling of CO2. Slab and coupled CCSM3 simulations that include the reductions of the other atmospheric trace gases and the large ice sheets covering North America and Eurasia at LGM give cooling in agreement with proxy inferences and indicate that LGM CO2 explains about half of the global cooling at LGM. Regional signatures of the climate system to changed LGM forcing are also an important measure of climate sensitivity and results from the fully coupled version of CCSM3 will be shown.
DE: 9604 Cenozoic
DE: 6620 Science policy
DE: 3337 Numerical modeling and data assimilation
DE: 3344 Paleoclimatology
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting