What's a Grand Solar Minimum Anyway? Why wasn't I taught about it i...

Grand Solar Minima occur when several solar cycles exhibit lesser than average activity for decades or centuries. Solar cycles still occur during these grand solar minimum periods but are at a lower intensity than usual. Grand Solar Minima have shown some correlation with global and regional climate changes.
A list of historical Grand minima of solar activity[9] includes also Grand minima ca. 690 AD, 360 BC, 770 BC, 1390 BC, 2860 BC, 3340 BC, 3500 BC, 3630 BC, 3940 BC, 4230 BC, 4330 BC, 5260 BC, 5460 BC, 5620 BC, 5710 BC, 5990 BC, 6220 BC, 6400 BC, 7040 BC, 7310 BC, 7520 BC, 8220 BC, 9170 BC.

Solar minimum events and approximate dates
Event Start End
Homeric minimum [8] 950BC 800BC
Oort minimum (see Medieval Warm Period) 1040 1080
Medieval maximum (see Medieval Warm Period) 1100-1250
Wolf minimum 1280-1350
Spörer Minimum 1450-1550
Maunder Minimum 1645-1715
Dalton Minimum 1790-1820
Glassberg Minimum 1880-1914
Modern Maximum 1914-2007
Modern Minimum (Eddy Minimum) 2007-
https://en.wikipedia.org/wiki/Solar_minimum#Grand_solar_minima_and_maxima

Global cooling is the central theory presented in Casey's Cold Sun and Dark Winter. Casey's theory, in particular, revolves around the belief that industrial CO2 emission is not severe enough to cause a change in earth's climate and that climate change is entirely impacted by the sun. Dark Winter also makes note that global climate cooling would begin approximately 3–14 years past Casey's initial discovery.
According to Casey, the earth is currently going through an interglacial warm period, a rare time of reprieve from an otherwise cold earth. This period of warmth essentially serves as Casey's explanation for the exponential growth of human civilization in the past few millennia. Moreover, Casey makes note that this period of warmth and prosperity, according to his calculation, is on the brink of ending.
Casey's theory also emphasizes the importance of sunspot patterns in determining the sun's effect on earth's climate. His belief is that the numerous sunspot patterns that have been observed throughout earth's history have affected the global climate in various ways. Casey's theory is that the sun is currently within a 206-year cycle and that a drastic cycle change is imminent. He believes this cycle change will lead to the severe cooling down of the earth.
Another central point in Casey's global cooling theory is the lack of counter strategy in regards to the advent of an ice age. Casey states that "solar hibernation" is ultimately inevitable and that the sun will continue to cycle into its next stage regardless of the actions of the common man. https://en.wikipedia.org/wiki/John_Casey_(climate_change_author)
The Dark Winter Is Coming:

"After applying the latest big data technique to six 2,000 year-long proxy-temperature series we cannot confirm that recent warming is anything but natural – what might have occurred anyway, even if there was no industrial revolution.There are, however, multiple lines of evidence indicating it was about a degree warmer across Europe during the MWP – corresponding with the 1200 AD rise in our Northern Hemisphere composite. In fact, there are oodles of published technical papers based on proxy records that provide a relatively warm temperature profile for this period. This was before the Little Ice Age when it was too cold to inhabit http://www.sciencedirect.com/science/article/pii/S2214242817300426
http://www.climatedepot.com/2017/08/22/new-study-multiple-lines-of-evidence-show-medieval-warm-period-was-warmer-than-today/"
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Greenland Ice Core Data Graph