Letter | Published:

The past, present and future of African dust

Nature volume 531, pages 493495 (24 March 2016) | Download Citation

Abstract

African dust emission and transport exhibits variability on diurnal1 to decadal2 timescales and is known to influence processes such as Amazon productivity3, Atlantic climate modes4, regional atmospheric composition and radiative balance5 and precipitation in the Sahel6. To elucidate the role of African dust in the climate system, it is necessary to understand the factors governing its emission and transport. However, African dust is correlated with seemingly disparate atmospheric phenomena, including the El Niño/Southern Oscillation7,8, the North Atlantic Oscillation9, the meridional position of the intertropical convergence zone10,11, Sahelian rainfall8 and surface temperatures over the Sahara Desert12, all of which obfuscate the connection between dust and climate. Here we show that the surface wind field responsible for most of the variability in North African dust emission reflects the topography of the Sahara, owing to orographic acceleration of the surface flow. As such, the correlations between dust and various climate phenomena probably arise from the projection of the winds associated with these phenomena onto an orographically controlled pattern of wind variability. A 161-year time series of dust from 1851 to 2011, created by projecting this wind field pattern onto surface winds from a historical reanalysis13, suggests that the highest concentrations of dust occurred from the 1910s to the 1940s and the 1970s to the 1980s, and that there have been three periods of persistent anomalously low dust concentrations—in the 1860s, 1950s and 2000s. Projections of the wind pattern onto climate models give a statistically significant downward trend in African dust emission and transport as greenhouse gas concentrations increase over the twenty-first century, potentially associated with a slow-down of the tropical circulation. Such a dust feedback, which is not represented in climate models, may be of benefit to human and ecosystem health in West Africa via improved air quality14 and increased rainfall6. This feedback may also enhance warming of the tropical North Atlantic15, which would make the basin more suitable for hurricane formation and growth16.

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Acknowledgements

This work was supported by the Agence Nationale de la Recherche (ANR) grant ANR-10-LABX-18-01 of the national Programme Investissements d’Avenir provided by the Laboratoire d’excellence Institut Pierre Simon Laplace (L-IPSL). We appreciate comments from our colleagues.

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Affiliations

  1. Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

    • Amato T. Evan
  2. Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS)/IPSL, UPMC Université Paris 06, Sorbonne Université, UVSQ, CNRS, Paris, France

    • Amato T. Evan
    • , Cyrille Flamant
    •  & Marco Gaetani
  3. CNRM-GAME, UMR 3589 CNRS and Météo-France, Toulouse, France

    • Françoise Guichard

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Contributions

A.T.E. carried out the main analysis and wrote the manuscript. F.G. analysed wind speed data from weather stations. All authors designed the study, discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Amato T. Evan.

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https://doi.org/10.1038/nature17149

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