How much it might vary is very difficult to tell, but for instance, it is clear that from the Pliocene to the
Quaternary (the last ~ 2,5 million years of
ice age cycles), the
climate has become more sensitive to orbital forcing.
To an Earth - system scientist the difference between the
Quaternary period (which includes the Holocene) and the Neogene, which came before it, is not just what was living where, or what the sea level was; it is that in the Neogene the
climate stayed stable whereas in the
Quaternary it swung in and out of a series of
ice ages.