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Research Article

Climate change in the Fertile Crescent and implications of the recent Syrian drought

Colin P. Kelley, Shahrzad Mohtadi, Mark A. Cane, Richard Seager, and Yochanan Kushnir
  1. aUniversity of California, Santa Barbara, CA 93106;
  2. bSchool of International and Public Affairs, Columbia University, New York, NY 10027; and
  3. cLamont–Doherty Earth Observatory, Columbia University, Palisades, NY 10964

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PNAS March 17, 2015 112 (11) 3241-3246; first published March 2, 2015; https://doi.org/10.1073/pnas.1421533112
Colin P. Kelley
aUniversity of California, Santa Barbara, CA 93106;
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  • For correspondence: colin.kelley@geog.ucsb.edu
Shahrzad Mohtadi
bSchool of International and Public Affairs, Columbia University, New York, NY 10027; and
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Mark A. Cane
cLamont–Doherty Earth Observatory, Columbia University, Palisades, NY 10964
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Richard Seager
cLamont–Doherty Earth Observatory, Columbia University, Palisades, NY 10964
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Yochanan Kushnir
cLamont–Doherty Earth Observatory, Columbia University, Palisades, NY 10964
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  1. Edited by Brian John Hoskins, Imperial College London, London, United Kingdom, and approved January 30, 2015 (received for review November 16, 2014)

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Significance

There is evidence that the 2007−2010 drought contributed to the conflict in Syria. It was the worst drought in the instrumental record, causing widespread crop failure and a mass migration of farming families to urban centers. Century-long observed trends in precipitation, temperature, and sea-level pressure, supported by climate model results, strongly suggest that anthropogenic forcing has increased the probability of severe and persistent droughts in this region, and made the occurrence of a 3-year drought as severe as that of 2007−2010 2 to 3 times more likely than by natural variability alone. We conclude that human influences on the climate system are implicated in the current Syrian conflict.

Abstract

Before the Syrian uprising that began in 2011, the greater Fertile Crescent experienced the most severe drought in the instrumental record. For Syria, a country marked by poor governance and unsustainable agricultural and environmental policies, the drought had a catalytic effect, contributing to political unrest. We show that the recent decrease in Syrian precipitation is a combination of natural variability and a long-term drying trend, and the unusual severity of the observed drought is here shown to be highly unlikely without this trend. Precipitation changes in Syria are linked to rising mean sea-level pressure in the Eastern Mediterranean, which also shows a long-term trend. There has been also a long-term warming trend in the Eastern Mediterranean, adding to the drawdown of soil moisture. No natural cause is apparent for these trends, whereas the observed drying and warming are consistent with model studies of the response to increases in greenhouse gases. Furthermore, model studies show an increasingly drier and hotter future mean climate for the Eastern Mediterranean. Analyses of observations and model simulations indicate that a drought of the severity and duration of the recent Syrian drought, which is implicated in the current conflict, has become more than twice as likely as a consequence of human interference in the climate system.

  • drought
  • Syria
  • climate change
  • unrest
  • conflict

Footnotes

  • ↵1To whom correspondence should be addressed. Email: colin.kelley{at}geog.ucsb.edu.
  • Author contributions: C.P.K., S.M., M.A.C., R.S., and Y.K. designed research; C.P.K. performed research; C.P.K., S.M., M.A.C., R.S., and Y.K. analyzed data; and C.P.K., S.M., M.A.C., R.S., and Y.K. 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.1421533112/-/DCSupplemental.

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Climate change and the recent Syrian drought
Colin P. Kelley, Shahrzad Mohtadi, Mark A. Cane, Richard Seager, Yochanan Kushnir
Proceedings of the National Academy of Sciences Mar 2015, 112 (11) 3241-3246; DOI: 10.1073/pnas.1421533112

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Climate change and the recent Syrian drought
Colin P. Kelley, Shahrzad Mohtadi, Mark A. Cane, Richard Seager, Yochanan Kushnir
Proceedings of the National Academy of Sciences Mar 2015, 112 (11) 3241-3246; DOI: 10.1073/pnas.1421533112
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  • Earth, Atmospheric, and Planetary Sciences
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Proceedings of the National Academy of Sciences: 112 (11)
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  • Article
    • Abstract
    • Heightened Vulnerability and the Effects of the Drought
    • The Drought in Context
    • Regional Climate Variability and Trend
    • Frequency of Multiyear Droughts
    • Mechanisms
    • Summary
    • Materials and Methods
    • Acknowledgments
    • Footnotes
    • References
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