I agree with Dara's argument and examples. In particular, even if one does find external linkages, unless one can forecast *those* behaviors, it won't help much.
That is why I am more satisfied with the approach that I am taking; the SOI sloshing model has 3 external forcing factors that are at least quasi-predictable -- i.e. quasi-biennial oscillations, Chandler wobble, and solar cycles. Each of these has a "watch out what's coming" predictability.