Finally, it looks as if the GSM is on.
First, this is not a 100% conformation that the Next Grand Solar Minimum has already begun, even though the data strongly indicates that the trends will continue according to the models of Zharkova et al, 2015, Ole Humlum 2011 John Casey and many others. The different models vary in duration. (see details in the introduction to the next Grand Solar Minimum.)
On June 12, 2019 NASA announced:
Solar Activity Forecast for Next Decade Favorable for Exploration
“The forecast for the next solar cycle says it will be the weakest of the last 200 years. The maximum of this next cycle – measured in terms of sunspot number, a standard measure of solar activity level – could be 30 to 50% lower than the most recent one. The results show that the next cycle will start in 2020 and reach its maximum in 2025.”
The beginning of a Grand Solar Minimum can only be definitely declared after several very low solar cycles (11- year-cycles or Schwabe cycles). A decline of 30- 50% in sunspot numbers already brings us to Dalton Minimum levels.
It must also be said that the Dalton Minimum itself is by some astronomers declared to have been only an incomplete Grand Solar Minimum . (Usoskin et al, 2011,) [iii]
Compare the current state of the sun to the Dalton Minimum conditions. Here, I added a sketch of the NASA projection to the end of the solar cycle progression of the last 400 years.
This graph compares the current solar progression to that of the Dalton Minimum. Original Graph by Anthony Watts / December 20, 2010. I added the recorded Solar Cycle 24 (green) and the NASA projection of solar cycle 25 (black dotted line). The similarities are striking.
“The Dalton Minimum was a period of low solar activity, named after the English meteorologist John Dalton, lasting from about 1790 to 1830. Like the Maunder Minimum and Spörer Minimum, the Dalton Minimum coincided with a period of lower-than-average global temperatures. The Oberlach Station in Germany, for example, experienced a 2.0°C decline over 20 years. The Year Without a Summer, in 1816, also occurred during the Dalton Minimum. Solar cycles 5 and 6, as shown below, were greatly reduced in amplitude.” Antony Watts.