The 11-year sunspot cycle number 24 has just ended. We are entering sunspot cycle 25. The number of sunspots has been decreasing over the past 3 cycles which has been about 4 decades. See plot below.
Note cycles 20 to 22, with an increase in peak sunspot number, is the same period that global warming has been claimed to be most significant . Then from cycle 22 to cycle 24 we see a decrease, but also there have been reports of global cooling, most significantly in the last decade or so.
On this plot the year 2020 shows the minimum number of sunspots. For the year 2019 the average number of sunspots was about 3.6. There were times when there were none, even in 2016. In 2020 we expect to see an increase as we enter the next cycle of solar activity.
We are now in February 2020 which is a year further past this plot. But it clearly shows cycle 24.
Now you might have read John L. Casey’s book “Dark Winter” (published in 2014) wherein he predicted
“that the sunspot count would not be greater than 74 — half what NASA was saying!”John L. Casey “Dark Winter” 2014, page 134.
How has that worked out? Based on the smoothed 13-monthly average the peak value was about 75 sunspots in cycle 24. This is pretty close. The maximum was in 2014 with a peak number of 113 sunspots. Casey predicted the peak in 2012.
The smoothed Australian Bureau of Meteorology (BOM) data predict about 86 sunspots by the end of 2021. This is much higher than John L. Casey’s prediction of about 50 for the next cycle number 25. But we’ll see what the annual average comes out to.
Thus the next 11 years (or even less) will tell us how good Casey’s prediction was.