EPS 201 CLIMATE 2

EPS 201 CLIMATE 2 - Lecture Notes April 14, 2009...

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Lecture Notes – April 14, 2009 Milankovich Cycles Changes Controlling Short-Term Climate Changes Lecture begins with an analysis of a graph in which the d 18 O concentration in biosediments varies over time, indicating a cyclic change in temperature/ice volume. From this we can see that there are three cycles in the climate on the following intervals: 1-5 million years 100,000 years 40,000 years 20,000 years Folks prior to Milankovich knew that there were changes in the Earth’s orbit that might have a reason for these cycles. Aside from angle of insolation is not the only cause of variations of climate. If we view the solar system from above, we can see that the Earth’s orbit is slightly elliptical – the shape of the orbit, however, changes over long periods of time. It turns out that because of the gravitational attraction of the large planets, there is an effect on the shape of the orbit of earth. Dr. Maya puts up three images showing eccentricity, obliquity, and precession. Eccentricity is a change in ellipticity, meaning that sometimes the orbit is more elliptical than at other times. Thus, there are orbits in which the earth can come closer to the sun, or orbits where the earth can be farther from the sun at other times. Obliquity refers to the change in the angle of the axis, which varies from 22.1° to 24.5° in the image she displays. This has an effect on the angle of insolation. Precession refers to the change in orientation of the axis, which looked at from “above” (i.e., looking down on the North Pole) would describe a counter-clockwise circle.
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Handout includes an image highlighting eccentricity – shows how in the more elliptical orbit there is a greater seasonal difference than in the less elliptical orbit,
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EPS 201 CLIMATE 2 - Lecture Notes April 14, 2009...

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