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The causality analysis of climate change and large-scale human crisis

  1. Yulun Anc
  1. aDepartment of Geography and
  2. bThe International Centre of China Development Studies, University of Hong Kong, Hong Kong;
  3. cSchool of Geographic and Environmental Sciences, Guizhou Normal University, Guizhou 550001, China;
  4. dDepartment of Finance, Jinan University, Guangzhou 510632, China;
  5. eDepartment of Geography, South China Normal University, Guangzhou 510631, China; and
  6. fSouth China Morning Post, Causeway Bay, Hong Kong

  1. Edited by Charles S. Spencer, American Museum of Natural History, New York, NY, and approved September 6, 2011 (received for review March 17, 2011)

Abstract

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.

Footnotes

  • ↵1To whom correspondence should be addressed. E-mail: zhangd{at}hkucc.hku.hk.

  • Author contributions: D.D.Z. designed research; D.D.Z., H.F.L., and B.L. performed research; D.D.Z., H.F.L., C.W., Q.P., and Y.A. analyzed data; and D.D.Z., H.F.L., and J.Z. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1104268108/-/DCSupplemental.

Freely available online through the PNAS open access option.

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