A longstanding question in paleoclimatology is how the periodic changes in
the Earth's orbit aroung the sun, which are known to be related to glacial
cycles, actually cause the onset of ice ages. Shackleton (2000) reports new
evidence showing that the orbital changes somehow lead to changes in atmospheric
CO2 which in turn modifies the greenhouse effect which then regulates the
expansion and contraction of ice sheets. He has found that orbital variations
themselves cannot directly lead to variations in ice volume, but that
intermediate mechanism of sufficient magnitude to control global temperatures
and thereby the equatorward advance and poleward retreat of ice sheets. Kerr
(200) provides a summary of the Shakleton (2000) paper.
Kerr, R.A., 2000: Ice, mud point to CO2 role in glacial cycle.
Science 289, 1868
Shackleton, N.J., 2000: The 100,000-year ice age cycle identified and found
to lag temperature, carbon dioxide, and orbital eccentricity. Science
289, 1897-1902
Return to Unit 1-4:
Atmospheric Composition, Carbon Dioxide
Return to Unit 1-5: Carbon
Cycle, Methane
Return to Unit
2-7: Paleoclimate; Ice Core and Lake Sediment Records