Guest essay by Jim Goodridge, former California State Climatologist
Hidden in the sunspot numbers are long-term trends. See the graph below.
Orbiting observatories since 1978 show solar irradiance and sunspot number are associated.
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.
Thanks to Dr. Leif Svalgaard for help in revising sunspot numbers.