Anthropogenic Global Warming Theory doesn't really have enough track record to judge.
Very true.
There's little doubt that the Earth has been warming.
"Little doubt" leaves a lot of room for interpretation (both objectively and subjectively). For the sake of argument, I'm willing to accept the premise, though the conclusion does appear to be time and location dependent.
there's little doubt that CO2 is a warming agent
CO2 is by definition a greenhouse gas and therefore can absorb and re-radiate "heat." How much and to what degree that influences surface temperatures or climate forcings is much more complicated.
human activity has increased its atmospheric concentration.
I think it would be more accurate to say that human activity has resulted in the emissions of CO2. Increases in CO2 concentrations depend on the performance of sources and sinks, many of which have substantial error bars.
No theory should be used a basis for public policy unless its reliability can be determined.
I couldn''t have stated it better.
Take care.
A very good observation. I don't know what the evidence is, if any, that measured CO2 increases are primarily due to human activity. Information about recent history is probably very good (we know how much fossil and other fuels are burnt and we know what atmospheric CO2 concentrations are) so we can reliably say today what the natural sinks and sources are doing in the aggregate, even if we can't identify and understand them in detail. But extrapolating that aggregate behavior into the future seems very chancy. As evidence, it's my understanding that we have inferred significant historical swings in CO2 concentrations which cannot have been due to human action.
Supposing those inferences are reliable, and supposing they cover siginficant historical periods, I'd trust that extrapolation into the future. You could add that variability as another uncertainty into the models.