HR: 08:15h
AN: PP51G-02 INVITED     [Abstracts]
TI: A new 1500-year climate reconstruction: enhanced low-frequency variability and the fingerprint of anthropogenic warming
AU: * Pollack, H N
EM: hpollack@umich.edu
AF: University of Michigan, Department of Geological Sciences, Ann Arbor, MI 48105-1005 United States
AU: Hegerl, G C
EM: hegerl@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences, Durham, NC 27708-0227 United States
AU: Crowley, T J
EM: tcrowley@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences, Durham, NC 27708-0227 United States
AU: Allen, M R
EM: m.allen1@physics.ox.ac.uk
AF: University of Oxford, Department of Physics, Oxford, OX1 3PU United Kingdom
AU: Hyde, W T
EM: wthyde@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences, Durham, NC 27708-0227 United States
AU: Smerdon, J E
EM: jsmerdon@ldeo.columbia.edu
AF: University of Michigan, Department of Geological Sciences, Ann Arbor, MI 48105-1005 United States
AU: Zorita, E
EM: Eduardo.Zorita@gkss.de
AF: GKSS-Research Center, Institute for Coastal Research, Geesthacht, 21502 Germany
AB: We present a new 1500-year temperature history for extra-tropical continental regions in the northern hemisphere. This reconstruction is based on a novel method that calibrates annually or decadally resolved proxy time series to instrumental temperature without loss of low-frequency variance. The calibration method takes into account noise and uncertainty in both proxy and instrumental data through application of a total least squares fitting procedure. Tests of this reconstruction technique with model-derived synthetic proxy data generated by the ECHO-G climate model show that the synthetic proxies capture the model temperature variability very well. The reconstruction derived from real proxy data shows excellent correlation with decadally-smoothed instrumental data over the calibration interval. The new reconstruction shows a broad warm interval peaking in the early 11th century, a slow cooling that reaches a minimum in the 17th century, and a subsequent warming that accelerates dramatically in the 20th century. Multi-decadal departures from these long-term trends also appear, but no past warm intervals exceed mid-20th century temperatures. The 17th-century minimum was about 1 K cooler than mid-20th century temperatures. These long-period characteristics of the new reconstruction also agree very well with a surface temperature history derived from subsurface temperature profiles in boreholes distributed over the same spatial domain. Detection and attribution ("fingerprint") analyses reveal that most of the late 20th-century warming and a substantial fraction of the warming in the first half of the 20th-century are anthropogenic, and suggest an equilibrium sensitivity to independently reconstructed forcings of about 2.5 K.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 4215 Climate and interannual variability (1616, 1635, 3305, 3309, 4513)
DE: 4902 Anthropogenic effects (1803, 4802)
DE: 4928 Global climate models (1626, 3337)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005