What’s Wrong with this Theory?
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If Milankovic was right, we should be able to see a pattern of past glaciations followed by deglaciation. Looking at sediment cores for the Pleistocene epoch, we find that the temperature cools by four to ten degrees every 40,000 to 100,000 years and then warms back up again. |
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GEOS 416 class notes |
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news for Milankovic, but there are two problems. • When conditions are favorable for an ice age in the northern hemisphere, they’re not favorable for one in the southern hemisphere. How could the Milankovitch Cycles cause a global change in climate then? • Milankovitch cycles can only account for a temperature difference of 1° to 2°. How is it possible then that sediment records show temperature differences of 7° to 10°? |
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Currently, scientists believe that once an ice age has been triggered, oceanic circulation currents can change and the mixing of the oceans cools the southern hemisphere. As glaciers begin to accumulate in the northern hemisphere, solar heat is reflected off the snow which leads to further cooling. Another theory is that the 100,000 year periodicity we see is the addition of the precession and obliquity cycles and not the eccentricity cycle at all. |
Exit Glacier |
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