In this paper, Professor Brooke summarizes key arguments in his book manuscript, A Rough Journey: Human History on a Volatile Earth (Cambridge University Press, in preparation), to describe the fundamental patterns of climate change over the eight thousand years between the emergence of advanced agricultural societies in the Middle to Late Neolithic and the eve of the Industrial Revolution. Generally, historians have assumed that climate change was a minimal background feature of human existence, so chaotic and indeterminable that it could be safely set aside in interpretive models. The new work in historical climate science, however, has reached a rigor, specificity, and scale that now permits the reconstruction of past climates in virtually every context of significant human occupation.
The result is that since the Mid-Holocene 6000-3000BC we can now describe a series of fundamental episodes of abrupt and deep climate change, interrupting broad climate optima. These optima and intervening episodes of crisis can be described in terms of a relatively simple and recurring set of relationships involving the impact of solar fluctuations and volcanic activity on the Asian monsoon, the ENSO system, the Siberian High, and the impact of NAO/AO fluctuations on the winter westerly jet stream. As a number of scholars are arguing, rather than constantly struggling at the technical bounds of subsistence, large-scale ancient societies were reasonably sustainable, and collapsed only under in the context of severe natural adversity. Rather than endogenous pressures, exogenous forces determined the fate of human numbers in a long antiquity.
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