February 28, 2007
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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 12, NUMBER 3, MARCH 1999
A 0.5-Million-Year Record of Millennial-Scale Climate Variability in
the North Atlantic, J. F. McManus, D. W. Oppo, and J. L. Cullen,Science
283 (5404), 971-975 (1999).
Examination of continuous high-resolution marine sediment records of the
subpolar North Atlantic shows the millennial-scale pacing of climate
variability. A critical threshold of ice sheet size, iceberg discharge,
and proxies of sea-surface conditions (the relative abundance of ice-raft
debris and the benthic oxygen isotope of planktonic Foraminifera) show
that only small ice-volume changes are associated with large-amplitude
shifts in climate response and variability.
124,000-Year Periodicity in Terrestrial Vegetation Change During the
Late Pliocene Epoch, K. J. Willis, A. Kleczkowski, and S. J.
Crowhurst,Nature 397, 685-688 (1999).
Spectral analysis of the lake sediments from Pula maar in Hungary
provide a high-resolution continental record of late-Pliocene climate
change (from 3 million to 2.6 million years ago) and the vegetative
response during this period of global cooling. The analysis indicates a
response of the terrestrial vegetation that has the same periodicities as
the Earths obliquity and precession. It also shows a very strong
response with a periodicity of about 124,000 years, a periodicity that
would not reflect solar forcing. Rather, internally driven nonlinear
responses of the climate system must have produced these vegetative
responses that were even stronger than the solar forcing.
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