Everyone hold your breath!!!
No-one knows how the centuries-long waxing and waning of the Sun works. However, astronomers now have space telescopes studying the Sun in detail.
This sentence really encapsulates the basic flaw with the entire man-made global warming supposition. Earth's climate is very complex with elements of atmosphere, inner earth dynamics, ocean movements and sun activity playing a role. To what extent we can measure or control or manipulate to achieve a desired effect is unknown.
The bottom line is that we have no idea what we can do to make the earth warm or cool with any certainty by implementing man-made activities. At this point, all we know for sure is that we might make it better, we might make it worse, or we might have no effect.