@bob_the_fisherman Said
Or even more accurately, the sun is responsible for the heat on earth that keeps us all living, and it's effect on global climate is a virtual unknown - the sun's heat is not a constant, nor is it's production of radiation.
Take the "mini ice age" event of... the 1700s I think. Scientists who study the sun's effect on climate thought the reason for the cooling was a lack of sun spot activity (that they think operates on something like an 11 year cycle, but possibly within bigger cycles), but it turned out that the reason sun spot activity may have been low was
possibly because of volcanic activity that increased atmospheric co2 significantly and led to global cooling (although there's no reason to assume there was not also a reduction in sun spot activity that may or may not have had an impact on global temps).
The reality is that there are too many variables, many of which we do not yet know, to take the alarmism seriously.
That's a new one on me ... Earth's volcanic activity reduced sunspots for +50 years? Got a link for that?
In broad, general terms: During "Solar Max" (high period of sunspots) the solar winds increase.
This causes the earth's atmosphere to compress a little bit, and compressing a gas causes it to heat up.
If sunspots / solar cycle were to be the cause of the current rise in global temperatures, then we should have seen a relative cooling during the solar minimums, which we are not.
In other words, during the current "Deep Trough" of sunspot activity, we should see the global temperature decrease, and we are not.
Also, during solar minimums, when the Earths atmosphere expands a little bit, it increases drag on low orbit satellites which must be accounted for.
And solar maxes protect us more from cosmic rays.
And yes - approximately 11 years +/- for a full cycle.
They determine which cycle a sunspot is in by it's polarity.
As for variance in the sun's output:
If you care to believe NASA.
So it is misleading to say the effect is "Unknown"