Only problem is that a Modern Grand Maximum did not occur and therefore sunspot activity cannot account for changes in climate since the commencement of the industrial revolution.
"The new correction of the sunspot number, called the Sunspot Number Version 2.0, led by Frédéric Clette (Director of the World Data Centre [WDC]–SILSO), Ed Cliver (National Solar Observatory) and Leif Svalgaard (Stanford University, California, USA), nullifies the claim that there has been a Modern Grand Maximum.
The results, presented at the IAU XXIX General Assembly in Honolulu, Hawai`i yesterday, make it difficult to explain the observed changes in the climate that started in the 18th century and extended through the industrial revolution to the 20th century as being significantly influenced by natural solar trends.
"solar activity appears to have remained relatively stable since the 1700s"
