Actually, it’s not a theory: the Sun has been shown to have a minor variability range of ~2-3%, and low sunspot counts have consistently correlated with a minima in solar flux.
Furthermore, astronomical records from the past two major minima (the Maunder and the Dalton) also correlate with historic “Little Ice Ages”, via multiple methods. Less detailed records also correlate high sunspot activity with higher solar flux: records from observations during the Medieval Climate Optimum also correlate high sunspot count with increase solar flux.
Sunspots are obviously not the cause, but ARE an indicator. . .
The theory I’m talking about isn’t about the sunspots - I haven’t a clue about the sunspots themselves. My complaint is about the correlation to what’s happening on Game of Thrones - I know a lot about geek stuff ;)