> Anthropogenic GHGs are nothing but uncontrolled geo-engineering, and either we can predict their effects accurately or not (spoiler: we can't). If we can, then we can predict the effects of other forms of geo-engineering comparably accurately.
Without addressing the first sentence or its "spoiler" (preserved only for context), the second doesn't follow: our ability (or inability) to predict the effects of GHG emissions in the ranges relevant to evaluating the effect of actual and reasonably-possible human actions with regard to them do not really have much bearing on, say, our ability (or inability) to project the impact of changes to (for example) solar energy input that are outside of past experience.
Without addressing the first sentence or its "spoiler" (preserved only for context), the second doesn't follow: our ability (or inability) to predict the effects of GHG emissions in the ranges relevant to evaluating the effect of actual and reasonably-possible human actions with regard to them do not really have much bearing on, say, our ability (or inability) to project the impact of changes to (for example) solar energy input that are outside of past experience.