Is There Evidence Linking CO2 to Warming?

Does it matter that there is not one piece of scientific evidence that links CO2 to warming in any sort of causality? Lots of conjecture, lots of statistical linkage — but no clear causal mechanism that I have been able to find.

Think about it in common-sense terms: why would something at roughly four hundredths of a percent by volume matter more than water vapor at around five percent? CO2 is a great fertilizer, and in my view not much more than that.

(This is my skeptic's argument as I wrote it at the time; it runs against the scientific consensus on the role of CO2 in warming.)