@RABEL222,
Quote:Why dont you choose a time period?
OK... lets choose a time period where the big factors affecting Global Climate Changes will actually themselves change, thus causing change in the climate .
The true shaker and mover of Ice Ages seems to be the solar systems movement up and down in the spiral arm of the galaxy . This puts a periodicity for Ice Ages of about 150 million years and a generally colder period lasting for 10's of millions of years .
Finger nails grow at the same pace as the continents move . So probably a 100,000 time period for those ... Ocean currents are dictated by the continents and temp differentials but are also suspected of being subject to rapid fluctuation through mechanisms not understood . So 100,000 yrs is a good start, but we should keep in mind it could be as little as a 100 period followed by an indeterminate period before it corrects itself and returns to the previous state . Also related to continental movement are mountain ranges . To make a measurable difference, these should also be taken as a 100,000 yr period .
The Milankovitch Cycle has its most effect on Glacial Advances and Retreats within an Ice Age and are due to variations in the Earth's orbit and axis that take it further or closer to the sun about every 20,000 and 40,000 years .
A solar cycle which does not affect climate, is roughly 11 years .
The Little Ice Age lasted about 300 yrs and may have been due to Ocean Currents or increased volcanic activity . The Medieval Warm period affected the Northern Hemisphere and has no known cause . Both these events go some way to discounting even talking about a Global Climate having minor variations as local variations of climate can be quite substantial and not affect the "Global Climate" .
So for Climate variation, the big picture is 150 million year period with the impact of that altered by "local conditions such as continents, oceans currents and mountains of the shortest possible time being 100,000 years . Within that, volcanoes as well as impact events can do whatever they want and have major effects, and on an even shorter scale, we have Milankovitch cycles of 40,000 and 20,000 years . Within those we have solar cycles of 11 years .
The smallest you can count on occurring regularly is a 100,000 year time period influenced by smaller peaks and troughs from those discussed above . How much would a 100,000 year cycle influence climate ? It may be so small as to be immeasurable . To have enough build up to make a difference GLOBALLY, we may need a million year time period .