Astronomical factors 1
 

Climate change mechanisms

Mechanical, thermodynamical, biological and human factors combined through times to bring about the climatic changes whose main result is the present Saharan aridity.
The most important of these factors are those stated by Milutin Milankovitch in his "astronomical theory" (Milankovitch 1920, 1941). This Serbian mathematician stated that, at a planetary scale, temporal and geographical climate variations are linked to insolation, which fluctuates according to the position of the Earth to the Sun. The succession of the seasons is caused by the angle of the polar axis and by the annual ecliptic revolution, but the general succession of the glacial and interglacial periods (corresponding to arid and humid periods in the Sahara) positioned at much more considerable intervals, is caused by what could be called "astronomical seasons" linked to three main factors:

1 -variation in the eccentricity of the Earth orbit,
2 -variation of the obliquity,
3 -precession of the equinox.

  The tilt of Earth's axis in its annual orbit around the Sun causes the Northern and Southern hemispheres to lean directly toward and then away from the Sun at different times of the year.
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