Recent studies have shown strong temporal correlations between past climate changes and societal crises. However, the specific causal mechanisms underlying this relation have not been addressed. We explored quantitative responses of 14 fine-grained agro-ecological, socioeconomic, and demographic variables to climate fluctuations from A.D. 1500–1800 in Europe. Results show that cooling from A.D. 1560–1660 caused successive agro-ecological, socioeconomic, and demographic catastrophes, leading to the General Crisis of the Seventeenth Century. We identified a set of causal linkages between climate change and human crisis. Using temperature data and climate-driven economic variables, we simulated the alternation of defined “golden” and “dark” ages in Europe and the Northern Hemisphere during the past millennium. Our findings indicate that climate change was the ultimate cause, and climate-driven economic downturn was the direct cause, of large-scale human crises in preindustrial Europe and the Northern Hemisphere.

Pei, Q., and D. D. Zhang. 2014. Long-term relationship between climate change and nomadic migration in historical China. Ecology and Society 19(2): 68. https://doi.org/10.5751/ES-06528-190268

Aim: The long‐term cyclical patterns of China's geopolitical shifts are of great interest to scholars and the public, but to date there has been no satisfactory explanation for the alternating occupancy patterns of the country's pastoral and agrarian polities. We fill this gap by differentiating the agroecological settings of these polities over time and quantitatively analysing the relationships between climate change and historical geopolitical variations.Location: China.Methods: Our dataset comprised 38 palaeohydroclimate reconstructions, the historical boundaries of China's empire and the changes in its size, and 1028 wars and 2737 battle locations over the past 2300 years. China‐wide precipitation during the period was reconstructed using the ‘weighted composite plus scale’ method. Time‐series analyses were performed to identify the strength of the associations between climate change and the geopolitical variables. Granger causality analysis and wavelet analysis were performed to verify the hypothesized causal links. Wavelet analysis was also used to identify the possible interactions (i.e. frequencies, significance, consistency and synchrony) between the signal components of the climatic and geopolitical variables at different temporal scales.Results: China's mean precipitation fell into three multicentennial cycles. The geopolitical variables corresponded to those cycles in the imperial era. The spatial–temporal frequencies of the boundaries and size of the agriculturalist empires and its frontiers with pastoralist empires were regulated by the long‐term (low‐frequency) precipitation fluctuations at the multicentennial scale. Wars of aggression were an important explanatory factor driving the land‐occupancy patterns of the two ecoempires under climate change, and caused most of the territorial shifts. Short‐term (high‐frequency) geopolitical changes were not associated with climate change.Main conclusions: Precipitation‐induced ecological change was an important factor governing the macrogeopolitical cycles in imperial China. Long‐term territorial expansion favoured the polity (agriculturalist or pastoralist) that was better adapted to the changing ecological conditions in the country's heartland.

Historical climatology is an interdisciplinary field of research encompassing the reconstruction of past climate and weather from written sources and artifacts, as well the application of climate reconstructions to the study of human history. Historical climatology has grown in recent years, and this growth has brought both insights and challenges. Research has expanded into new regions and periods and diversified into novel sources, methods, and interdisciplinary collaborations. At the same time, the heterogeneity of evidence and approaches has complicated the integration of multiple climate and weather reconstructions. Moreover, the diversity of disciplinary perspectives, terminologies, and perspectives can create miscommunication among scholars in the field, particularly on issues of historical knowledge and causation. Innovative approaches in the field, including Bayesian methods, may help address these challenges.This article is categorized under: Climate, History, Society, Culture > Disciplinary Perspectives Climate, History, Society, Culture > World Historical Perspectives Assessing Impacts of Climate Change > Representing Uncertainty The Social Status of Climate Change Knowledge > Knowledge and Practice