Societal responses to El Nino-related climate extremes in southern Africa

Context:
The El Niño Southern Oscillation (ENSO) is a primary influence upon tropical and sub-tropical climates at interannual timescales. Models of future climate change suggest that the nature of ENSO events is likely to alter during the 21st century, with the tropical Pacific either shifting abruptly to a more positive ENSO (El Niño) phase or evolving into an 'El Niño-like' mean state. A change towards more prolonged El Niño conditions will have far-reaching impacts, especially in southern Africa where El Niño events are frequently associated with drought. The strongest impacts occur in the southeast of the subcontinent, where c.20% of summer rainfall variance is accounted for by ENSO modulation. Any increase in ENSO-related drought duration, superimposed upon projected decreases in annual rainfall due to global warming, will have major implications for human livelihoods.

Much research has been undertaken into the impacts of 20th century droughts upon southern African communities. However, little is known about the repercussions of climate extremes during previous centuries, the ways in which communities responded to such periods of environmental stress, and, significantly, the socio-economic factors that may have influenced vulnerability over time. Analyses of historical documents, coupled with climate model simulations, can provide powerful insights into rainfall variability and any associated societal repercussions during periods of extreme climate. Documents charting technological adaptation, narrative and myth with respect to rainfall variability have been used, for example, to investigate how different sectors of society responded to, and articulated knowledge about, periods of unusual climate. When interpreted in the context of economic, political and demographic changes, such information can provide a guide to where critical sensitivities to future climate change may lie.

Crucially, historical documents can also provide information on spatio-temporal rainfall variations. These data can be compiled, analysed to identify relative precipitation levels and incorporated into climate models to produce regional syntheses of large scale climate during El Niño events. This provides the context within which any historical socio-economic adaptations can be interpreted. Studies of the 19th century are particularly relevant as the period predates recent anthropogenic-atmospheric impacts and includes at least 25 El Niño events.

Objectives:
The aim of this proposal is to examine the socio-economic consequences of, and human responses to, climatic extremes associated with El Niño events in southern Africa during the 19th century. It will achieve this by:
1 Identifying the spatio-temporal evolution of climate extremes associated with 19th century ENSO episodes using historical documentary sources combined with climate modelling;
2. Identifying the scale of impact and nature of human responses to these extreme climatic conditions using historical documentary sources;
3. Examining how societal responses to climate variability changed over the 19th century, and exploring any socio-political changes that may have influenced resilience and vulnerability.
The project will focus upon reconstructing climatic conditions and associated human responses in KwaZulu-Natal (South Africa), Madagascar and Malawi. These areas have been selected as they all (i) lie within the area of greatest ENSO-sensitivity in southern Africa, (ii) experience significant ENSO-related modulation of summer rainfall, (iii) have distinctive colonial and pre-colonial histories, (iv) have limited available climate information prior to the instrumental period, yet (v) have considerable 19th century documentary materials from which to reconstruct climate histories.

Results from the project have so far been published in nine papers:

NASH, D.J. & Hannaford, M.J. (2020) Historical climatology in Africa: A state of the art. PAGES News 28: 10-11.

NASH, D.J., Klein, J., Endfield, G.H., Pribyl, K., Adamson, G.C.D. & Grab, S.W. (2019) Narratives of nineteenth century drought in southern Africa in different historical source types. Climatic Change 152: 467-485.

Brázdil, R., Kiss, A., Luterbacher, J., NASH, D.J. & Řezníčková, L. (2018) Documentary data and the study of past droughts: A global state of the art. Climate of the Past 14: 1915-1960.

NASH, D.J., Pribyl, K., Endfield, G.H., Klein, J. & Adamson, G.C.D. (2018) Rainfall variability over Malawi during the late nineteenth century. International Journal of Climatology 38 (Suppl. 1): e629-e642.

Klein, J., NASH, D.J., Pribyl, K., Endfield, G.H. & Hannaford, M. (2018) Climate, conflict and society: changing responses to weather extremes in nineteenth century Zululand. Environment and History 24: 377-401.

Hannaford, M. & Nash, D.J. (2016) Climate, history, society over the last millennium in southeast Africa. WIREs Climate Change https://onlinelibrary.wiley.com/doi/abs/10.1002/wcc.389.

NASH, D.J., Pribyl, K., Klein, J., Neukom, R., Endfield, G.H., Adamson, G.C.D. & Kniveton, D.R. (2016) Seasonal rainfall variability in southeast Africa during the nineteenth century reconstructed from documentary sources. Climatic Change 134: 605-619.

NASH, D.J., Pribyl. K., Klein, J., Endfield, G.H., Kniveton, D.R. & Adamson, G.C.D. (2015) Tropical cyclone activity over Madagascar during the late nineteenth century. International Journal of Climatology 35: 3249-3261.

NASH, D.J. & Adamson, G.C.D. (2014) Recent advances in the historical climatology of the tropics and subtropics. Bulletin of the American Meteorological Society 95: 131-146.