Solar Cycle 24 continues to become less active. The June 2017 International Sunspot 30 day average number was 19.4. The maximum for Solar Cycle 24 occurred April 2014 at 116.4. The following chart illustrates how the solar cycle activity has dropped off. Solar Cycle 21 was larger than 22 which was larger than 23 which was larger than the current Solar Cycle 24.
The three charts above were posted on WUWT website titled “Trends in the Revised Sunspot Number Dataset“. From that posting comes the following analysis:
Sunspots have increased by 1 percent per year since 1700. This suggests recovery from the Little Ice Age of 1660 to 1710. A major increase in sunspot trend was observed from 1940 to 2002.
This is coinciding with the atmospheric CO2 increase. This suggests that the temperature-CO2 correlation is spurious, rather than causal.
Examining the top chart from the WUWT posting—“Annual Sunspot Number”– Solar Cycle 19 was the most active Sunspot Cycle ever. The chart —-“Accumulated Departure From Average Sunspot Numbers”—also shows that the Sun’s increasing activity from 1940 to 2002 is unmatched over the period 1700 to date. This coincides with the increase in global temperatures.
Sunspots are a proxy for solar activity. From Climate4you comes the following:
“Since sunspots are darker than the surrounding photosphere it might be expected that more sunspots would lead to less solar radiation and a decreased solar constant. However, the surrounding margins of sunspots are hotter than the average, and so are brighter; overall, more sunspots increase the sun’s solar constant or brightness.
The variation caused by the sunspot cycle to solar output is relatively small, on the order of 0.1% of the solar constant (a peak-to-trough range of 1.3 W/m2 compared to 1366 W/m2 for the average solar constant).”
The following chart shows the solar irradiance and Sunspots for Cycles 21, 22 and 23.
Irradiance is pretty much discounted by many solar scientist as to having a major effect on climate change. That doesn’t mean that the Sun isn’t the major factor in the Earth’s temperature, but that it is too steady to be involved in the minor swings were are currently experiencing. However, the correlation of Sunspots to total irradiance seems to be very close.
When you look at this chart of solar irradiance since 1610*, it appears to tell us that it does propel the minor swings.
For the last item on this posting, the solar polar fields are shown below. The technique of predicting the NEXT solar cycle would suggest that Solar Cycle will be about the same size as Solar Cycle 24. Solen.com summarizes the technique as
“The development of the solar polar field strength throughout a solar sunspot cycle can be used to predict the magnitude of the next cycle and the peak of the current cycle. Polar field reversals typically occur within a year of sunspot maximum. It is not uncommon for the northern and southern polar fields to have significant differences in field strength and develop asynchronously over time. The Wilcox Solar Observatory has been collecting solar polar field data since 1975 .
Looking at the black line on the chart shows that it is slightly smaller than that same line exiting Solar Cycle 23 which predicted Solar Cycle 24 would be smaller than its predecessor. Hence with the current black line being smaller in amplitude, it would be predicting that 25 will be the same or smaller size than Solar Cycle 24.
*Solar irradiance for the most of the chart is reconstructed by proxies. The ability to accurately measure solar irradiance at the top of the Earth’s atmosphere is a recent thing. The era of scientific satellites allowed this measurement to be made very accurately.