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3. Energy Variation
The Earth's orbit shape changes over periods of about 100,000 years
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The eccentricity of the Earth's orbit is a 100,000 year cycle varying between 0 and 0.06 and is therefore still close to circular even when most eccentric. At it's most extreme, eccentricity is responsible for a change of approximately 0.2% in the annual amount of incoming solar radiation. Although small, this change in radiation in the more eccentric orbits produce relatively large differences between the positions where the Earth is closest, and farthest from the sun. In the most eccentric orbit the difference between the radiation received in the closest and farthest sun - Earth distances is estimated at 30%, and there are extreme differences between seasons. In the present orbit the Earth is closest to the sun in late December and farthest from the sun in late June.
By how much does the Earth's orbit shape change?