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Read Full Article (file size: 331258 bytes) Cited by
PALEOCEANOGRAPHY,
VOL. 23,
PA3202,
doi:10.1029/2007PA001512,
2008
Mid-Holocene ENSO: Issues in quantitative model-proxy data comparisons
J. Brown
Department of Meteorology, University of Reading, Reading, UK
A. W. Tudhope
School of Geosciences, University of Edinburgh, Edinburgh, UK
M. Collins
Hadley Centre for Climate Prediction and Research, Met Office, Exeter, UK
H. V. McGregor
School of Earth and Environmental Sciences, University of Wollongong, Wollongong, New South Wales, Australia Institute of Environmental Research, Australian Nuclear Science and Technology Organisation, Menai, New South Wales, Australia
Abstract
Evaluation of climate model simulations using observed data contributes to the assessment of confidence in model predictions
of future climate change. The mid-Holocene represents an opportunity to evaluate model simulations of El Niño–Southern Oscillation
(ENSO) in comparison with coral proxy evidence of reduced ENSO amplitude. Quantitative comparisons between coral records and
model output have been limited by (1) the use of different measures of ENSO amplitude, (2) possible sampling of natural variability
in short records, and (3) uncertainty about the stationarity of the relationship between central Pacific sea surface temperature
(SST) variability and ENSO signals at the coral site. We examine these issues using modern and fossil coral records from the
western Pacific and model simulations of preindustrial and mid-Holocene climate. As a measure of ENSO amplitude, the standard
deviation is found to be preferable to event frequency or size as event-based measures are highly dependent on the choice
of threshold and may be unreliable for a small number of events. Model ENSO amplitude is found to be strongly dependent on
the choice of averaging period, with calendar year averages smoothing the seasonal ENSO signal. A relatively robust relationship
between SST variability in the NINO3.4 region and the ENSO SST and precipitation anomalies archived in corals is demonstrated
for the instrumental period and for a set of model simulations. Remaining uncertainty about changes in ENSO teleconnections
under paleoclimate conditions implies the need for additional proxy records from ENSO-sensitive regions before quantitative
reconstructions of ENSO amplitude can be used to evaluate model sensitivity.
Received 28
June
2007;
accepted 21
April
2008;
published 9
July
2008.
Keywords: El Niño;
climate models;
coral.
Index Terms: 4922 Paleoceanography: El Nino (4522); 4928 Paleoceanography: Global climate models (1626, 3337); 4916 Paleoceanography: Corals (4220); 4215 Oceanography: General: Climate and interannual variability (1616, 1635, 3305, 3309, 4513); 4934 Paleoceanography: Insolation forcing.
Read Full Article (file size: 331258 bytes) Cited by
Citation: Brown, J., A. W. Tudhope, M. Collins, and H. V. McGregor
(2008),
Mid-Holocene ENSO: Issues in quantitative model-proxy data comparisons,
Paleoceanography,
23,
PA3202,
doi:10.1029/2007PA001512.
Copyright 2008 by the American Geophysical Union.
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