Did many years of "history".. never happen?!
There has been a stable and persistent cycle of 200 years warming and 200 years cooling for at least the past 1,800 years. Unusual events like comet dust or a major volcanic eruption are not needed to explain the wave-like behavior of civilization over time. (Such things happen, but are incidental and/or have the same - cosmic - cause.)
Official History has been at pains - and gone through some absurd contortions - to obscure this.
[Note: Events of 375 - 500 actually took place from 375 - 400, and Dark Ages was 400 not 500 years. In other words, it's been closer to 1,800 years than 2,016 years since year one of the Current Era (CE/"AD").]
1 - 200: Warming
The Roman Empire is doing well, expanding and stable.
200 - 400: Cooling
Food production declines, Roman Empire spread too thin, fractures into East & West. By 375, growing season gets too short in Northern part of temperate zone to sustain tribes, Volkerwanderung/"wandering of peoples" (deliberately misleading), hundreds of thousands of (hungry) people all descending on Roman Empire en masse from N. Europe & N. Central Asia (Huns).
By 400, W. Roman Empire ceases to exist qua Roman Empire.
400 - 600: Warming (corresponds to 500 - 700 of Official History)
First half of "Dark Ages." Warming period could have enabled increased food production leading to increase in population in Europe (as happened later), but recent collapse of civilization meant they could not take advantage of it.
The Muslims took advantage of it by expanding rapidly throughout the Middle East, across N. Africa, and up into Spain.
600 - 800: Cooling (corresponds to 700 - early 900's of Official history)
In the first half of this cooling period, Charles Martel stopped the Islamic expansion into France, and his grandson Charlemagne followed on from this by conquering France, Germany, and N. Italy. As the cooling continued, however, Charlemagne's progeny were not able to hold his empire together.
By the end of the first century of this cooling period, the Vikings had begun their raiding, driven south by lack of food. The progressing cold in their homelands pushed them farther and farther South and East (to Constantinople) throughout the 2nd century of the period; many Vikings switched from raiding to settling down, esp. in the British Isles & N. France.
800 - 1000: Warming (corresponds to mid 900's - 1200 of Official History)
The vaunted Medieval Warm Period (MWP). Charlemagne's conquering had Christianized most of W. Europe, restoring some stability relative to the immediate post-collapse era. Thus, they were able to make use of the warming this time, greatly increasing food supply & more than doubling the population.
By the end of this warming period, the Vikings had settled Greenland (h/t Razib Khan for this link, via @hbdchick), and reached N. America.
1000 - 1200: Cooling (corresponds to 1200 - 1400 of Official History)
For nearly the first half of this cooling period, Europeans (esp. Western) rode the momentum of the Medieval Warm Period. By the "1290's" (of the Official Chronology), that had run out, and the situation went bad fast.
The 2nd half of this cooling period ("the 1300's"/actually 1100's) is described by modern historians as "disastrous", "horrific", and a time of "crisis" & "catastrophe". I suspect some significant minority of the deaths attributed to the Black Death were directly and/or indirectly from the drastic drop in food supply, itself directly caused by the cooling, which was quite severe by 3/4's the way through this 200 year period.
It was also the time when the "Hundred Years War" started; the Official History will only admit to social and economic causes, usually downplaying or ignoring the cold weather.
1200 - 1400: Warming (corresponds to 1400 - 1600 of Official History)
The first half of this warming period saw the Renaissance, starting in Italy.
In the 2nd half of this warming period, the Europeans began sailing all over the earth.
1400 - 1600: Cooling (corresponds to 1600 - 1800 of Official History)
Again, like with the first century of cooling after the MWP, the European peoples were enjoying the momentum from the previous warming period as the planet began cooling. And again, throughout the 2nd half of the cooling, as cold weather decreased food production, social & economic pressures continued to build up on the governments of the day. This led to the American and French revolutions. (Think of the famous painting of George Washington standing in the boat, with boulder-sized chunks of ice floating in the river.)
The use of the term "Little Ice Age" is (again, deliberately) misleading, as it implies an unusual - or at least very rare - occurrence. In fact, as you've just seen, it is quite usual. There is this 200 year cooling period every 400 years - if not always as severe as the most recent one.
1600 - 1800: Warming (corresponds to 1800 - 2000 of official History)
The warming of the first half of this 200 year period gave us the Industrial Revolution, with the 2nd half corresponding to what we've all been taught to call "the 20th century."
The Global Warming hysteria/hoax has been a psychological warfare operation by the "Elites" to mis-direct our attention from exactly what this article is about.
1800 - 2000: Cooling (corresponds to 2000 - 2200 of Official Timeline)
We have only just begun a 200 year cooling period..
Have you ever noticed that almost all the paintings, drawings, carvings, etc. - every kind of visual representation - from the Dark Ages until about 300 years ago depicting historical events is allegedly anywhere from decades to centuries after the fact?
Go ahead, look!
BC / BCE
If this cycle of 200 years of warming/200 years of cooling has been stable for 2000 years, then the transition of the Roman Republic into the Roman Empire would have been final 1/4th of a 200 year cooling period.
If the cycle has been stable for over 3000 years, the collapse of the Bronze Age civilization would have been right at the end of a 200 year cooling period. As the Arctic circle descended upon N. Europe, that would have pushed people living there down into S. Europe, which would have in turn pushed (at least some of) the people living in S. Europe at the time into the Mediterranean - to become the Sea Peoples.