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Posted on 02/12/2008 3:58:13 AM PST by raybbr
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The Earth's Changing OrbitIf the earth and the sun were the only bodies in the solar system, the earth's orbit would not change. However, the moon and the other planets are constantly pulling on the earth. The result is that the angle between the earth's axis and the plane of its orbit, the season at which the earth is closest to the sun, and the degree to which the earth's orbit is elongated all vary slowly over time. Right now, the elongation of the orbit (the eccentricity) is rather small -- about 1.7%. This results in the sun being about 7% brighter at the earth when it is closest, on January 4, than when it is most distant.
by Sue Ann Bowling
June 15, 1987
Alaska Science Forum
Twelve thousand years ago, when the glaciers of the last great ice age were melting, the eccentricity was a bit higher, about 2%. At the same time, the earth was closest to the sun in June, and most distant in January, so the sun was about 7 % brighter in June than it is today. At various times in the last million years, however, the eccentricity has been much higher -- as much as 6%, which would make the sun almost 25% brighter at perihelion (when the earth is closest to the sun) than at aphelion (when the earth is farthest from the sun). During the interglacial before the last ice age, about 125,000 years ago, the eccentricity was about 4%. The times of largest eccentricity tend to be about 100,000 years apart.
On January 3 or 4 (it varies) the Earth is at its closest point to the sun (the perihelion), but because water heats up so slowly, it doesn't make as much difference in temperature in the southern hemisphere as it otherwise might.The southern hemisphere is cooler latitude for latitude, but its temperature is more stable. Anyway, Antarctica is the dryest continent, that is, it has the least precipitation. If southern hemisphere temperatures were warmer (say, if the aphelion and perihelion were reversed), the hydrologic cycle would change, there would be more precipitation, and Antarctica would wind up deeper in ice, as would places like northern Canada and Greenland. Oh, and furthermore, I say, Al Gore must be destroyed.
I would be more than happy to oblige...
Al Gore delenda est.
Seventh grade science. One grade ahead of Algore.
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