Seasonal rainfall variability in southeast Africa during the nineteenth century reconstructed from documentary sources
Analyses of historical patterns of rainfall variability are essential for understanding long-term changes in precipitation timing and distribution. Focussing on former Natal and Zululand (now KwaZulu-Natal, South Africa), this study presents the first combined annual and seasonal reconstruction of rainfall variability over southeast Africa for the 19th century. Analyses of documentary sources, including newspapers and colonial and missionary materials, indicate that the region was affected by severe or multi-year drought on eight occasions between 1836 and 1900 (the rainy seasons of 1836–38, 1861–63, 1865–66, 1868–70, 1876–79, 1883–85, 1886–90 and 1895–1900). Six severe or multi-year wet periods are also identified (1847–49, 1854–57, 1863–65, 1879–81, 1890–91 and 1892–94). The timing of these events agrees well with independent reconstructions of 19th century rainfall for other parts of the southern African summer rainfall zone (SRZ), suggesting subcontinental scale variability. Our results indicate that the relationship between El Niño and rainfall in southeast Africa was relatively stable, at least for the latter half of the 19th century. El Niño conditions appear to have had a more consistent modulating effect upon rainfall during the 19th century than La Niña. The rainfall chronology from this study is combined with other annually-resolved palaeoclimate records from mainland southern Africa and surrounding oceans as part of a multi-proxy rainfall reconstruction for the SRZ. This reconstruction confirms (i) the long-term importance of ENSO and Indian Ocean SSTs for modulating regional rainfall; and (ii) that summer precipitation has been declining progressively over the last 200 years.
KeywordsRainfall Variability Southern Oscillation Index Southern Annular Mode Documentary Source Southern Annular Mode Index
This research was funded by Leverhulme Trust Research Project Grant number F/00 504/D. We extend our thanks to the three expert reviewers, to the archivists for access to collections of materials, and to Stan Stanier for designing the ENSOAfrica database used for the storage of documentary evidence. RN is funded by the Swiss National Science Foundation (grant PZ00P2_154802).
- Gillett NP, Kell TD, Jones PD (2006) Regional climate impacts of the Southern Annular Mode. Geophys Res Lett 33. doi: 10.1029/2006GL027721
- Lindesay JA, Harrison MSJ, Haffner MP (1986) The Southern Oscillation and South African rainfall. S Afr J Sci 82:196–197Google Scholar
- Neukom R, del Rosario PM, Moyano R, et al. (2009) An extended network of documentary data from South America and its potential for quantitative precipitation reconstructions back to the 16th century. Geophys Res Lett 36. doi: 10.1029/2009gl038351
- Niang I, Ruppel OC, Abdrabo MA, et al. (2014) Africa. In: Barros VR, Field CB, Dokken DJ, et al. (eds) Climate change 2014: impacts, adaptation, and vulnerability. Part B: regional aspects. Cambridge University Press, Cambridge, pp. 1199–1265Google Scholar
- Nicholson SE (1981) The historical climatology of Africa. In: Wigley TML, Ingram MJ, Farmer G (eds) Climate and history. Cambridge University Press, Cambridge, pp. 249–270Google Scholar
- Rayner NA, Parker DE, Horton EB, et al. (2003) Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J Geophys Res-Atmos 108. doi: 10.1029/2002jd002670
- Reason CJC, Rouault M (2002) ENSO-like decadal variability and South African rainfall. Geophys Res Lett 29. doi: 10.1029/2002GL014663
- Schulze RE (2001) South African atlas of agrohydrology and climatology, Beta 1.002. University of KwaZulu-Natal, PietermaritzburgGoogle Scholar
- Tyson PD (1986) Climatic change and variability in southern Africa. Oxford University Press, Cape TownGoogle Scholar
- Washington R, Preston A (2006) Extreme wet years over southern Africa: role of Indian Ocean sea surface temperatures. J Geophys Res-Atmos 111. doi: 10.1029/2005jd006724
- Webb CB, Wright JB (2014) The James Stuart archive of recorded oral evidence relating to the history of the Zulu and neighbouring peoples. University of KwaZulu-Natal Press, DurbanGoogle Scholar
- Woodborne S, Hall G, Robertson I, et al. (2015) A 1000-year carbon isotope rainfall proxy record from South African baobab trees (Adansonia digitata L.). PLoS ONE:10. doi: 10.1371/journal.pone.0124202