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El Niņo and Food Security in Southern Africa
October 2009

Acknowledgements: FANRPAN acknowledges US Agency for International Development (USAID) as the source of this document: http://www.usaid.gov/


El Niņo is a phenomenon which occurs in the Pacific Ocean, but affects climate globally. This document summarizes the known historic impacts of El Niņo in southern Africa. The impact of El Niņo in the SADC region has varied significantly in its severity, though it generally has a greater impact in the southern half. The current El Niņo is classified as weak to moderate. The document explains how the possible climatic outcome might influence agricultural prospects and food security.

Understanding El Niņo

An El Nino can be defined as the appearance of warm sea surface temperature (SST) in the central and eastern Pacific Ocean off the coast of Peru and Ecuador. Specifically, it occurs when a three-month average SST anomaly exceeds 0.5oC. El Ninos are recurrent weather phenomena, occurring approximately every four to seven years, and usually lasting between 12 and 18 months. The last four El Ninos however, including the current one, have occurred every two to three years. These SST changes can drive major weather and climate fluctuations around the globe, which in turn have major consequences for food security. Therefore, understanding this relationship, and applying this knowledge to improved climate forecasts, is a valuable early warning tool.

The 1997/98 El Nino event (4oC above normal sea surface temperatures over the equatorial Pacific Ocean) was the strongest observed in the last 50 years of accurate data gathering. This warming, coupled with the warming of SSTs over the southwestern Indian Ocean, resulted in extreme weather conditions in the Greater Horn of Africa. Previous strong El Nino events have been less warm, with some events having SST anomalies of 2oC to 3oC above normal.

While El Ninos are strongly associated with climate anomalies, the impacts vary greatly between events. Important variables include how warm the SST gets, how large an area of the equatorial Pacific heats up, and the timing of the onset of the event. Six of the last nine El Nino events over the last 30 years were weak to moderate, and all produced varying impacts. The most intense El Ninos in the last 30 years occurred in 1982/83, 1991/92, and 1997/98. Despite the record strength of the 1997/98 El Nino, the impacts in many areas of southern Africa were not as severe as had been expected. This led forecasters to conclude that factors other than El Nino indices could have a significant bearing on the outcome of the rainfall season, even during an El Nino year. In particular, climate scientists concluded that the deviation from expected rainfall outcomes in 1997/98 was due to several global and regional-scale climate systems that were significantly different from previous El Nino events, and may have caused greater than usual precipitation in parts of Southern Africa.

From an agricultural perspective, one of the main impacts of El Nino in southern Africa is one or more prolonged dry spells at some time between January and March. Usually, the most-affected areas include the southern half of the SADC region, particularly Zimbabwe, southern Mozambique, Swaziland, South Africa, Botswana, and Namibia. These long dry spells usually come when rainfall is most required by crops (particularly cereals) and tend to lead to below-normal seasonal rainfall totals, thus negatively affecting crop production. In most of the recent El Niņo events, at least some areas in the southern half of the region were mildly to severely affected.

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