After some cursory research, I think I have figured out the cycle.
There seems to be a general cycle of warming and cooling every 1000 or 1200 years (500-600 years of cooling, 500-600 years of warming):
1900-1400 BC,
Middle Bronze Age Cold
1400-900 BC, Bronze Age Optimum
900-300 BC,
Iron Age Cold
300 BC-300 AD,
Roman Warm period
300-800 AD,
Dark Age Cooling
800-1300 AD,
Medieval Warm Period
1300-1800 AD,
The Little Ice Age
1800-2300? AD,
Global Warming
Ironically, it appears that warming periods are characterized by agricultural/industrial revolutions and increased fertility, while cold periods are usually dark eras with population scarcity. If only Climate Change was man-made, then we could create bountiful eras artificially!
There also seems to be another cycle of about 60 years (30 years cooling, 30 years warming), the last cycle lasted from about 1940-2000. From 1940-1970, there were just as many environmentalists warning of "Global Cooling" as of Global Warming. From 1970-2000, these cooling enthusiasts died out as the warming seemed to be growing without bound. After 2000, a "pause" in Global Warming has been declared, and the resulting cooling phase has renamed the phenomenon as "Climate Change".
Forbes on Global Cooling
Another article on Global Cooling
However, every 120 years or so this 30 year period becomes especially cold:
1050-1080, Oort Minimum
1170-1200, undiscovered minimum?
1290-1320,
Wolf Minimum
1410-1440, undiscovered minimum?
1530-1560,
Sporer Minimum
1650-1680,
Maunder MInimum
1790-1820,
Dalton Minimum
1940-1970,
Global Cooling
The next great cold spell should come in the 2060s, after a warming period from 2030-2060.
There is also an 11-year cycle for sunspots, which have an important effect on global temperatures. The last cycle lasted from about 1997-2008. The peak of the current cycle happened in 2013.
Article from NASA on sunspots
Another article on sunspots
Other solar cycles
Of course, there is always the 100,000 year
glacial cycle. The last Ice Age ended in 15,000 BC, and has been warming since then (hence the agricultural revolution in 10,000 BC, resulting in, among things, human civilization). The peak of this cycle will come in 35,000 AD, and the next Ice Age will come in 85,000 AD.
All in a days work, I suppose,
Nathan G