But I fully admit the difficulty to be very great.
I cannot see the full force of your difficulty of no known cause of a mundane change of temperature.

We know no cause of continental elevations and depressions, yet we admit them.

Can you believe, looking to Europe alone, that the intense cold, which must have prevailed when such gigantic glaciers extended on the plains of N.Italy, was due merely to changed positions of land within so recent a period?
I cannot.
It would be far too long a story, but it could, I think, be clearly shown that all our continents existed approximately in their present positions long before the Glacial period; which seems opposed to such gigantic geographical changes necessary to cause such a vast fall of temperature.

The Glacial period endured in Europe and North America whilst the level of the land oscillated in height fully 3,000 feet, and this does not look as if changed level was the cause of the Glacial period.

But I have written an unreasonably long discussion.