Evolution of some observed climate extremes in the West African Sahel

AbstractClimate variability and change affect most socioeconomic sectors in West Africa. It is now admitted that the variability of climate has increased since the 1950s mainly because of the increased concentration of anthropogenic greenhouse gases in the atmosphere. In this study, we analyze the evolution of some extreme temperature and precipitation indices over a large area of West Africa spanning from latitudes 10–25°N and longitudes 17°W–15°E. The results show a general warming trend throughout the region during the period from 1960 to 2010, namely through a negative trend in the number of cool nights, and more frequent warm days and warm spells. This was the case not only for locations inside the continent, but also for those in coastal areas. Trends in rainfall related indices are not as uniform as the ones in temperatures. Nevertheless, a general tendency of decreased annual total rainfall and maximum number of consecutive wet days characterizes the study period. The cumulated rainfall of extremely wet days shows a positive trend in most locations. As for the maximum number of consecutive wet days, it shows an overall decreasing trend from 1960 to the mid 1980s, but starting from the late 1980s, an increasing trend is observed in several locations, indicating that extreme rainfall events have become more frequent in the West African Sahel during the last decade, compared to the 1961–1990 period. Policy implications of these observed trends may include investment and promotion of low cost and environmentally friendly energy production systems, the redesign of infrastructure and production systems to account for higher risks of losses due to floods and/or droughts, and the promotion of research for more heat tolerant crop/animal species and cultivars/breeds