Demographic crises of different climate phases in preindustrial northern hemisphere

This research empirically analyzes the association between climate change, population size, and demographic crises as indicated by what we term “population checks,” or major wars, epidemics, and famines from AD 1000 to AD 1900 in the Northern Hemisphere based on historical records and climate reconstructions. We conducted this study at two temporal scales: (1) the entire study period of 900 years and (2) three climate phases according to temperature (cold, mild, and warm) of 300 years each. By adopting linear and nonlinear statistical methods, we found climate change and population size to have significant roles in driving the demographic crisis at the temporal scale of the entire study period. In terms of the three climate phases of 300 years each, we find that war is more closely correlated to climate change than to population size for all three phases. However, population size itself is more likely to trigger epidemics during mild and warm phases and is more important in relation to famines than climate change during all three climate phases. This study emphasizes the importance of scale in reviewing the social past in terms of climate change and population size. Empirical evidence of large-scale demographic crises within the three climate phases could also provide a timely reference for scientists or policymakers in addressing the potential effects of global warming. Copyright © 2020 Springer Science+Business Media, LLC, part of Springer Nature.