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Variations in the Earth's Orbit: Pacemaker of the Ice Ages [The Milankovitch theory validation] 1976

Autor: J. D. Hays, John Imbrie, N. J. Shackleton

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In stoc: Da

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Detalii produs Using ocean sediment cores, the authors tested the astronomical theory of Milutin Milankovitch
that oscillations in climate over the past few hundred thousand years are connected with Earth's
orbital variation around the Sun (Milankovitch cycles).

''In the spring of 1970, James D. Hays decided that the time had come to launch a new attack
on the ice-age problem. With the Pleistocene time scale fixed at several points by magnetic
reversals, and with paleontological techniques available to track ocean currents and to estimate
ocean temperatures, deep-sea cores had been transformed into instruments for monitoring
global climate. For the first time geologist could determine when-and to what extent-different
parts of the ocean changed during ice ages. If a more accurate time scale could be established
within the Brunhes Epoch, it would also be possible to make a definitive test of the Milankovitch
theory.

But five years of experience with cores from the Antarctic and Pacific Oceans had convinced
Hays that a satisfactory reconstruction of oceanic history was a task for any single investigator,
or any single institution. A team of paleontologist, mineralogists, geochemists, and geophysicist
would have to be formed [included James Shackleton measuring oxygen-isotope ratios, and
George Kukla]. Discussing this idea with John Imbrie at a launch counter near Columbia
University, Hays pointed out that the appropriate techniques were already being applied by
investigators working in dozen laboratories. All that was needed was an organization to
coordinate these independent efforts... But Imbrie expressed concern that such an
interinstitutional effort might be unmanageable. 'Don't worry,' Hays replied, 'all we need is money
for plane fares and telephone bills.'

Hays's optimism was justified... Named CLIMAP the project's first objective was to reconstruct
the history of the North Pacific and North Atlantic Oceans during the Brunhes Epoch. Financial
support came from the National Science Foundation's International Decade of Ocean Exploration
program IDOE... By 1977, expanditures totaled $6,630,500 [$30,000,000 today]...

Convinced now that major climatic changes were caused by astronomical variations, and that the
41,000-year and 23,000-year climatic cycles followed systematically behind variations in tilt and
precession, Hays, Imbrie, and Shackleton, announced their findings in an article in Science, which
appeared on December 10, 1976: Variation in the Earth's Orbit: Pacemaker of the Ice Ages.

A century after Croll published his theory and 50 years after Milankovitch mailed his radiation
curves to Koeppen and Wegener, two cores from the Indian Ocean confirmed the astronomical
theory of the ice ages. At last, geologist had clear evidence that the motions of the Earth in its
orbit arround the Sun triggered the succession of late Pleistocene ice ages. Exactly how this
triggering mechanism operated, and why the 100,000-year cycle of orbital eccentricity appeared to
be so strongly impressed on the climatic record of the last half-million years were still unknown.
But for the moment, it was enough to know that Milutin Milankovitch, traveler through distant world
and times, had led the way to solving a major part of the ice-age mistery.''

John Imbrie and Katherine Palmer Imbrie; Ice Ages. Solving the Mistery, 1979, pp. 161-173

It is interesting to note the final words, really scientific prophecies, of this highly influential paper:

''A model of future climate based on the observed orbital-climate relationships, but ignoring
anthropogenic effects, predicts that the long-term trend over the next several thousand years is
toward extensive Northern Hemisphere glaciation.''

(Hays, Imbrie, Shackleton 1976, p. 1131)

John Imbrie (1996) and N. J. Shackleton (2004) recieved the prestigious Vetlesen Prize.
The Vetlesen Prize was established in 1959 by the G. Unger Foundation, and was designed
to be the Nobel Prize of The Earth Sciences, awarded for 'scientific achievement resulting in
a clearer understanding of the Earth, its history, or its relations to the universe.'

''Variations in the Earth's Orbit: Pacemaker of the Ice Ages'', 1st Edition, in ''Science'' No. 4270
Vol. 194, 1976, pp. 1121-1132; Published by American Association for the Advancement of
Science; good condition.

Price: $ 50,000.00