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UCSB Geologist links earth orbit and climate
With an assist from
axial tilt and precession
By the University of California news
service
6 Apr 10 - (Santa Barbara, Calif.) –– In an analysis of the past 1.2
million years, UC Santa Barbara geologist Lorraine Lisiecki discovered a
pattern that connects the regular changes of the Earth's orbital cycle
to changes in the Earth's climate. The finding is reported in this
week's issue of the scientific journal Nature Geoscience.
Lisiecki performed her analysis of climate by examining ocean sediment
cores. These cores come from 57 locations around the world. By analyzing
sediments, scientists are able to chart the Earth's climate for millions
of years in the past. Lisiecki's contribution is the linking of the
climate record to the history of the Earth's orbit.
It is known that the Earth's orbit around the sun changes shape every
100,000 years. The orbit becomes either more round or more elliptical at
these intervals. The shape of the orbit is known as its "eccentricity."
A related aspect is the 41,000-year cycle in the tilt of the Earth's
axis.
Glaciation of the Earth also occurs every 100,000 years. Lisiecki found
that the timing of changes in climate and eccentricity coincided. "The
clear correlation between the timing of the change in orbit and the
change in the Earth's climate is strong evidence of a link between the
two," said Lisiecki. "It is unlikely that these events would not be
related to one another."
Besides finding a link between change in the shape of the orbit and the
onset of glaciation, Lisiecki found a surprising correlation. She
discovered that the largest glacial cycles occurred during the weakest
changes in the eccentricity of Earth's orbit - - and vice versa. She
found that the stronger changes in the Earth's orbit correlated to
weaker changes in climate. "This may mean that the Earth's climate has
internal instability in addition to sensitivity to changes in the
orbit," said Lisiecki.
She concludes that the pattern of climate change over the past million
years likely involves complicated interactions between different parts
of the climate system, as well as three different orbital systems. The
first two orbital systems are the orbit's eccentricity, and tilt. The
third is "precession," or a change in the orientation of the rotation
axis.
If you've read
"Not by Fire but by Ice," you know that this is what
I've been saying for
years.
See: UCSB geologist discovers pattern in Earth's long-term climate
record
http://www.eurekalert.org/pub_releases/2010-04/uoc--ugd040610.php
Thanks to Dr. Bill Wilden, Tim Kieler and Heather Cleary for this link
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