I don’t disagree Doc, it is a very interesting puzzle. Just thinking of the scales involved is amazing. Before the solar UV surprise, solar TSI change might cause 0.1 degree change. With expect 4.5 degrees fo warming, that would be insignificant. Now with 0.8 to 1.2 change due to CO2 doubling, 0.1 is pretty significant. The models estimate something like 10% changes due to natural internal variability. Of 4.5 that would be small, 0.45 degrees that would average out. Now, with potential much great solar impact, that is not something to be over looked.
So nailing a number with any model is unlikely. But, the temperature data is pretty good except for the poles. Physics is still physics. Just kick in a little more intense thermo and fluid dynamics and and we get closer. That is until something changes. That is the nature of a chaotic system, every new start can produce a different result.
So while not perfect, those simple boxes can go through a lot more new starts than a complex model that takes months to run. Simple is better when you need fast results. Right now, exciting stuff seems to be happening, so I want fast.