HR: 11:50h
AN: PP51D-07    [PDF]
TI: A Northern Hemisphere Climate Reconstruction through Integration of Borehole Temperature Data and a Conventional Proxy Model
AU: * Huang, S
EM: shaopeng@umich.edu
AF: The University of Michigan, Department of Geological Sciences, Ann Arbor, MI 48109-1063 United States
AB: Each disciplinary approach to a paleoclimate reconstruction has its own strengths and limitations in representing past climate variability. A reconstruction from borehole temperatures is more robust in detecting long-term variability than in retrieving high-frequency information. Conversely, a reconstruction from a traditional proxy approach usually offers a higher temporal resolution of relative changes along with a greater uncertainty in the long-term trend. Aided by a controlled simulation Zorita et al. (2003, J. Clim., v.16: 1378-1390) show that the technique employed by Mann et al. (1999, Geophy. Res. Lett, v.26: 759-762) for climate reconstructions can represent annual climate variability reasonably well, whereas it suffers from difficulties in reproducing the low-frequency behavior of the global temperature evolution even under favorable conditions. With annual climate variability captured in high resolution proxies and long-term information preserved in borehole temperatures (e.g., Huang et al., 2000, Nature, v.403: 756-758; Harris and Chapman, 2001, Geophys. Res. Lett., v.28: 747-750; Beltrami, 2003, Science, v.297: 206-207), it is desirable to develop a technique to integrate the two schools of information for a more complete picture of the past climate change. I present such an integrated reconstruction by inverting a composite subsurface temperature profile assembled from 697 boreholes from the Northern Hemisphere, with the annually resolved multi-proxy reconstruction of Mann et al. (1999) as the a priori model. The integrated reconstruction shows a net warming of around 1K and a delineation of two relatively cool periods over the last five centuries. Within the five-century interval the 17th century was the coolest and the 20th century the warmest. Temperatures dipped in the 19th century prior to the 20th century warming. The integration of the two bodies of information greatly improves the comparability of the reconstructed temperatures and the radiative forcing history. Regression analysis of the integrated reconstruction and an ensemble of natural and anthropogenic forcings suggests a greater sensitivity of climate to external forcings than previously estimated.
DE: 1600 GLOBAL CHANGE (New category)
DE: 1620 Climate dynamics (3309)
DE: 1645 Solid Earth
DE: 5418 Heat flow
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting