Quote:
Originally Posted by Tropo-Bob
There is a half-truth in this over the extremely-long term with respect to climate (as distinct from weather).
The Earth wobbles, thus the tropics shrink and expand over 40,000 years. The affect is that rainfall bands move up and down with the result being that the Sahara Desert can be grasslands, or just sand.
The Earth's orbit is not circular. It is not even a stable ellipse. The orbit goes from being near circular to more elliptical and back to circular over some 100,000 years. This means that the amount of heat from the Sun varies, as the Earth's distance varies more extremely than now during the course of the year; for thousands of years.
Then there's Procession over 26,000 years. I am bit uncertain with my understanding with this one, but it is said to affect climate in the long term.
Then off course, there are geological factors such as plates drifting.
I once read that the first 3 factors will combine to bring on a substantial Ice Age in aprox 60,000 years. (A bit like biorhythms coming together for a triple-critical day).
|
The orbital forcing of climate is called Milankovitch cycles. See
https://en.wikipedia.org/wiki/Milankovitch_cycles
and
https://en.wikipedia.org/wiki/Marine_isotope_stage