• Gravitational interactions with the other planets perturb the Earth's orbit.
• Resulting changes in the Earth's orbit have caused seasonal changes in the amount of solar radiation (at periods between 105-106 years).
• These radiation changes have regulated the growth and decay of global ice sheets over geologic time.

Evidence:

Early (late 1800's) astronomical observations showed that the Earth has a slow, regular wobble. Calculations showed that this wobbling could produce significant changes in the amount of radiation received in a given season.

Landmark paper:

Hays et al. (1976) - Used marine sediment records to document a statistically rigorous linkage between Glacial-Interglacial ice volume (d¹⁸O) changes and calculated variations in the Earth's orbit.

What is needed to understand the Milankovitch Mechanism:

• How d¹⁸O variations in foraminifera have recorded past changes in glacial ice volume.
• How changes in the Earth's orbit should affect the seasonal distribution of solar radiation.
• The conceptual link between orbital radiation forcing and high-latitude climate response....