Two special conditions of terrestrial landmass distribution, when they exist concurrently, appear as a sort of common denominator for the occurrence of very long-term simultaneous declines in both global temperature and atmospheric carbon dioxide (CO2):
1) the existence of a continuous continental landmass stretching from pole to pole, restricting free circulation of polar and tropical waters, and
2) the existence of a large (south) polar landmass capable of supporting thick glacial ice accumulations.
These special conditions existed during the Carboniferous Period, as they do today in our present Quaternary Period.
... Basically, ice ages seem to occur whenever a continuous continental landmass extends from one polar region to the other, blocking the free latitudinal circulation of ocean currents, while a large continent capable of supporting thick ice accumulations is situated over the south pole. These conditions existed 300 million years ago during the Carboniferous Period as they do for the Earth today. However for most of geologic history, the distribution of the continents across the globe did not satisfy this criteria....
