"...the "fallacy of exclusion" in which a *single* cause and effect relationship is presented as the only cause and effect relationship amongst *many* that may be at work in a system. This is a rhetorical trick, not a scientific argument."

A bit like attributing global warming solely to CO2, in fact.

"All the sub-systems within the planet-wide ecosystem are interconnected; change one and they all change. Problem is, we don't know to what degree and how."

Agreed; but one consequence of that logic is that it is dangerous to reduce (as if we could!) atmospheric CO2. Since "we don't know to what degree and how" that change will affect all other variables we could be doing more harm than good. It is the nature of a chaotic system (such as the planetary atmospheric-system) to be unpredictable; but all you warmistas seem so confident in your predictions of doom. Shome mishtake, surely.