"CO2 in concert with H2O keeps enough heat locked in to keep Earth warmer than the albedo temperature. That's proven science, so you're just being a curmudgeon to suggest otherwise."

Our Ocean moderates global temperature. And is overwhelmingly the dominate factor.

Without 70% of the area of the Global covered by ocean, Earth would be colder- the ocean absorbs far more sunlight energy than the land.
When talking about the atmosphere H2O and CO2 are dominate factors, but ocean is far more significant in regards to climate than the atmosphere.

"The significance of that tiny CO2 fraction lies in its stability. Water vapour is a condensible gas across all Earth's temperature range, while CO2 isn't. And water that has snowed out causes an albedo rise and temperature drop at an effective insolation level just a bit lower than the present day. No CO2 would cause such a runaway albedo rise and temperature drop - that's the Icehouse Earth scenario which is solidly evidenced in the late Pre-Cambrian."

When Earth has runaway to Icehouse, CO2 could very well be significant- if in high enough concentration- though I believe unlikely when below .1% of atmosphere. There is some question about how far Earth has runaway- were all the ocean permanently frozen- or were significant portions in the equator region left open. It is the equatorial region of the oceans the pump the most amount heat into our planet.
There are also other factor- and in particular solar activity which could be significant factor effecting this.