Don't think this is generating much interest, but it's still interesting
me, so I'm gonna keep going
Effects of the Little Ice Age
Many of the effects I am postulated are going to be largely drawn from the OTL Little Ice Age, or from the actual Ice Ages. What causes climate effects are poorly understood, and expect that with the Long Little Ice Age there will be a number of different fluctuations in different regions which will have different effects. Much of the world will be colder and drier that in OTL for the most part, though certainly not everywhere. From the point of view of humanity and it's civilization, certain regions will, in general be net losers, while others net winners. Things remain, climatically and historically, the same until roughly the middle of the 7th century, when global temperatures which had been slowly on the increase, begin a slow and steady decline.
Europe will be the biggest net loser. Throughout this period, northern Europe is going to be cold and dominated largely by thick pine forest, with populations shringing and becoming quite isolated. The winters will be long, and the summers short and plagued by hailstones. In Scotland, reindeer herding may increased in importance, while around the coasts of England the local fishermen will benefit from the increased yields of herring and cod migrating south. Scandinavia is probably going to be dominated by Saami types for a long period to come. Iceflows are going to make navigation in the northern seas a difficult prospect at best. In the absence of Norwegian expansion populations in the British Isles may be shifted around less, and the Picts are likely to survive. Invasions from the mainland may be a continued threat, however, particularly as the lowered temperatures occasionally cause the English channel to freeze over enough for armies to march directly from the continent. The absence of Varangians is going to mean that the Eastern Slavic culture will be far more influenced by the Khazars of the south.
The big winner is Northern Africa, able to yield absolutely as well as relatively higher yields than OTL. This will only be further enhanced by the Muslim Agricultural Revolution, and we will see North Africa becoming once again one of the most important and populaous regions of the Mediterranean. Even south of the Atlas mountains, where the effects will be less obvious, this will hold true. In general, the rate of desiccation will be slower than OTL, and West Africa somewhat wetter (particularly the Niger river and an expanded Lake Chad). This will mean earlier and more extensive contacts between flourishing North Africa and the gold-rich black kingdoms to the south, as well as increased likelihood of a state powerful enough to unite the Sahel and create a single trade zone between East and West Africa. In southwest Africa, dessication will be greater than OTL.
Another winner is the American southwest. As North America in general may become cool in some regions (though this is not necessarily the case, as in OTL during the Little Ice Age the climate in North America was quite warm), there will be a significant advantage to the Southwest in the absence of the great droughts that typified the period in OTL. The most likely beneficiaries are going to be the peoples of the Southwest, and their agriculture and urbanisation may be much more extensive than in OTL, and possibly maize agriculture could spread to California. In the south, the Yucatan is going to go through an earlier drought than OTL, but at a higher point in Mayan history. This could force changes to the Mayan society, or trigger a migration west at the expense of the declining Teotihuacan.
A loser of sorts is north Asia, which is going to see the population growth that occured during the Tang OTL to be much less pronounced. There likely will still be a population shift south, but the reduced population and increased southern typhoons are going to make Chinese power and culture projection toward the south more difficult. Indianized kingdoms like the Champas and other states such as the Nanzhao are going to be better positioned than in OTL to resist sinification and the power of the Chinese state. Though the threat from northern barbarians may be reduced due to lower populations amongst those peoples, the threat of the Gokturks and other Turkic peoples to the west is going to be more pronounced. Instead of a north-south orientation, the Chinese cultural mind may develop a more east-west viewpoint.
Glaciation will become quite extensive in a number of regions: Tibet, the Alps and the Andes in particular. The nascent Tibetan empire may collapse earlier than OTL in this timeline, while the development of Swiss culture is unlikely. In the Andes the glaciers as well as increased dessication caused by altered Pacific winds are going to retard the development of the civilizations there. Desertification will become a problem in a number of places. Central Asia and North-east India will become quite dessicated, with the Thar desert spreading further across the Aravallis toward the Ganges Valley. This will likely reduced the populations of these regions, perhaps even slowing the progress of Islam into both Central Asia and India. It may mean that the migrations of the Turkic peoples become more directly focused on a weaker China, and less likely to migrate into the Middle East (though Khazaria may remain fair game).
Monsoon effects are interesting. Reduced sea temperatures will result in a lessened monsoon effect on India. However, it is likely to become wetter and stormier in southern China and eastern Africa is likely to go through a long wet period (broken by occasional periods of dryness). Typhoons along the southern Chinese coast are going to make the development of maritime culture there more difficult, but not impossible. The North Pacific is going to be warmer than OTL. Throughout the world, there will be slightly lower sea levels as the ice pack slowly expands throughout this era. The Red Sea will become shallower and perhaps more difficult to navigate. In Russia, the expanding ice pack will cause the Ob and the Yenisey to form large lakes.