That’s sorta where I’m going, but I really don’t know much about the Science of the Sun.
I think that Sunspots have to do at least with the energy of the surface of the sun.
With the progress of remote Sun sensing in the last half Century, I’d guess that there are likely other observable characteristics that could provide measurements of Sun Energy below the level of Zer0 Sunspots, and thus extend the scale.
Got it. Observable with remote sensing - but not with the visual. I don’t know - I’m pretty sure those scientist’s have it ALL figured out by now! Well - at least the part where the sun doesn’t have much to do with global warming.