Fortunately, most of the other talks were of far higher caliber, utterly devastating to orthodoxy on a variety of issues. But UVB varies normally with latitude, twice as high in El Paso as in Minneapolis. Carbon dioxide, even in total, is a small player, so the effect of changes in carbon dioxide is even smaller. Sunspots cause variations in solar brightness. This provides a way to track pre-historic sunspot cycles.
Sunlike stars have starspots, just as the sun has sunspots.
Baliunas is one of the leading investigators of starspots. She is co-author of a recent article in Scientific American which presents studies of the spot cycles of many sunlike stars. Stars have Maunder minima too , and one has even been caught entering such a period when spots are rare. Studies of starspots have erased much of the mystery which used to surround sunspot cycles. Sunspot cycles are now fairly well understood.