When the cycles coincide

Each of these three cycles—of eccentricity, axial tilt, and "axial wobble" or precession of the equinoxes—has a very small effect by itself. (The diagram illustrates all three.) What would happen, however, if all three cycles were to coincide? Suppose that when the precession of the equinoxes places Earth farthest from the Sun during the Northern Hemisphere winter, the Earth's orbit is also at its greatest obliquity, so that the distance between Earth and the Sun is at a maximum. The two effects would reinforce each other, bringing very cold winters to the Northern Hemisphere. Suppose that the axial tilt was also at a maximum at this time. In midwinter, the Northern Hemisphere would be tilted farther away from

The three Milankovitch cycles. Three cyclical variations in the orbit and rotation of the Earth that trigger the onset and ending of glaciations.

Orbital stretch is a change in the eccentricity of the Earth's orbit. Axial tilt is the variation in the angle at which the north-south axis of the Earth is tilted with respect to the vertical. Axial wobble is the way the Earth's axis slowly turns around the vertical.

the Sun than it is now. This would reduce still further the amount of solar radiation it received.

This concentration on what happens in the Northern Hemisphere is relevant to the climatic consequences. There is much more land in the Northern Hemisphere than there is in the Southern Hemisphere. Its lower specific heat capacity means that in winter land loses heat much faster than the ocean does (see the explanation of specific heat capacity on pages 30-31). If land receives less solar radiation in winter, before the winter ends it will have cooled to a lower temperature than the ocean would have done under similar circumstances.

Adhemar and Croll

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  • Sophia
    When do all three milankovitch cycles coincide?
    7 years ago

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