Where do you think the water come from to make the two-mile high Ice Age icecap?
The oceans.
And which came first, the chicken or the egg?
The oceans.
(Monocellular life IS "an egg").
This is obvious and logical.
Photosynthetic life FIXED atmospheric CO2 as sea-floor carbonate deposits.
The Earth lost its CO2 blanket and froze to the equator, preventing the fixation of further CO2. The earth being coated with a thick skin of ice did NOT prevent vulcanism, however.
The volcanic CO2 in the atmosphere built to an excessive amount, melting Snowball Earth.
Seaborne photosynthetic organisms were once again able to fix carbon as carbonates, and very slowly temperatures lessened and Life migrated inland from the coastal margins and colonized inland, causing more carbon to be fixed, this time as FOSSIL FUEL deposits.
The low end of the Malenkovitch cycle tipped the atmosphere into an ice age when the reducing CO2 fell below a certain margin.
With this second ice age, once again the ability of Life to fix CO2 was diminished, and volcanic CO2 built up in the atmosphere.
This ice age thawed.
This is the general order of events, broken and modified both by the effects of huge vulcanism (Siberian Traps) and continental break-up and drift with the formation of high mountain ranges
*.
This is the point.
If we ALL thought like YOU do, Oxy, we're going to experience first the death of our civilization by global warming, then as savages we are going to experience the NEXT ice age.
OTHERWISE.
We will manage and maintain 350 parts per million carbon dioxide in our atmosphere in perpetuity, with neither tragedy ever threatening us again.
I put it to you, that in the first instance we will have proved that we are indeed merely apes.
In the second we will have proved ourselves to be essentially
human, and to be properly distinguished from our origins.
It is our test. Will you pass?
* Some things are independent of these events. The continual build-up of unstable methane clathrates in oceans and tundra, for instance.