The shape of the Earth's orbit varies between nearly circular (theoretically the eccentricity can hit zero) and mildly elliptical (highest eccentricity was 0.0679 in the last 250 million years). Eccentricity measures the departure of this ellipse from circularity.
The Earth's orbit approximates an ellipse. Land masses change temperature more quickly than oceans, because of the mixing of surface and deep water and the fact that soil has a lower volumetric heat capacity than water. Milankovitch emphasized the changes experienced at 65° north due to the great amount of land at that latitude. This is known as solar forcing (an example of radiative forcing). Milankovitch studied changes in these movements of the Earth, which alter the amount and location of solar radiation reaching the Earth. The combined effect of precession with eccentricity is that proximity to the Sun occurs during different astronomical seasons. Finally, the direction in the fixed stars pointed to by the Earth's axis changes ( axial precession), while the Earth's elliptical orbit around the Sun rotates ( apsidal precession). A greater tilt makes the seasons more extreme. In addition, the rotational tilt of the Earth (its obliquity) changes slightly. When the orbit is more elongated, there is more variation in the distance between the Earth and the Sun, and in the amount of Solar Radiation, at different times in the year. The Earth's orbit varies between nearly circular and mildly elliptical (its eccentricity varies). Orbit with 0.5 eccentricity, exaggerated for illustration Earth's orbit is only slightly eccentric The variations are complex, but a few cycles are dominant. The Earth's rotation around its axis, and revolution around the Sun, evolve over time due to gravitational interactions with other bodies in the Solar System. In the 1920s, he hypothesized that variations in eccentricity, axial tilt, and precession combined to result in cyclical variations in the intra-annual and latitudinal distribution of solar radiation at the Earth's surface, and that this orbital forcing strongly influenced the Earth's climatic patterns. The term was coined and named after Serbian geophysicist and astronomer Milutin Milanković. Milankovitch cycles describe the collective effects of changes in the Earth's movements on its climate over thousands of years. Vertical gray line shows present (2000 CE).Ocean sediment and Antarctic ice strata record ancient sea levels and temperatures:.Precession index and obliquity control insolation at each latitude:ĭaily-average insolation at top of atmosphere on summer solstice ( Q ¯ d a y ) at 65° N.
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