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3. Energy Variation
Precession alters the distribution of radiation across the surface of the Earth
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As with tilt, the effects of precession cannot alter the amount of solar radiation received by the Earth, however, precession does alter the way in which radiation is distributed across the surface of the Earth. It has already been seen that the present-day combinations of tilt and eccentricity reinforce each other in the southern hemisphere (producing hotter summers, colder winters) and oppose each other in the northern hemisphere (so moderating the differences between summer and winter). Precession simply reverses these combinations; tilt and eccentricity reinforce each other in the northern hemisphere, and oppose each other in the southern hemisphere. Hence precession alternatively produces more, or less, extreme seasons in each hemisphere on a cycle of approximately 23,000 years.
How does precession affect radiation distribution?