Oribital Variations
Slow changes in the Earth’s orbit lead to small but climatically important changes in the strength of the seasons over tens of thousands of years. Climate feedbacks amplify these small changes, thereby producing ice ages.
Eccentricity
Earth’s orbit oscillates very slightly between nearly circular and more elongated every 100,000 years. This cycle is evident in the glacial/interglacial cycles of roughly the same period.
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Orbital Eccentricity
The Earth's orbital path varies in the degree to which it is circular. This change in its "eccentricity" varies between 0.00 and 0.06 on a 100,000 year cycle. When the eccentricity equals 0.00 the orbital path is circular and when it is 0.06 the orbital path is slightly elliptical. The current value is 0.0167. |
Tilt
The Earth spins around an axis that is tilted from perpendicular to the plane in which the Earth orbits the Sun. This tilt causes the seasons. At the height of the Northern Hemisphere winter the North Pole is tilted away from the Sun, while in the summer it is tilted toward the Sun. The angle of the tilt varies between 22° and 24.5° on a cycle of 41,000 years. When the tilt angle is high, the polar regions receive less solar radiation than normal in winter and more in summer.
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Earth's Tilt
The Earth is tilted from perpendicular in its orientation to the Sun. This tilt varies from 22° to 24.5° on a 41,000 year cycle. The current tilt is 23.3°. |
Wobble
There is a slow wobble in the Earth’s spin axis, which causes the peak of winter to occur at different points along the Earth’s elliptical orbital path. This variation in the seasons occurs on an approximately 23,000-year cycle.
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Wobble of the Earth's Spin Axis
The Earth's axis of rotation wobbles like a top on a 23,000 year cycle. This causes the Earth's seasons to reach their maximum at different distances from the Sun due to the elliptical shape of the Earth's orbit. |
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