In all fairness, the Sun had extended periods of no spots not that long ago. However, that was in spotless days that were a fraction of a year.
The Maunder Minimum (1645–1715) lasted 70 years.
The Maunder Minimum roughly coincided with the *middle part* of the Little Ice Age. The current best hypothesis for the cause of the Little Ice Age is that it was the result of volcanic action. Mount Rinjani in Indonesia on the island of Lombok in particular, in 1257.
The Little Ice Age is thought to have started from 1300-1500 AD, and ended around 1850.
However, this is puzzling, as two of the largest eruptions in human history also happened in Indonesia, Mount Tambora in 1815 and Kraktatoa in 1883. That is, one 35 years *before the end* of the Little Ice Age, and one 33 years after the end of the LIA.
So, the bottom line is, like with MMGW, they are just guessing.
Hekla