Senegal: Climate Overview
Map of Senegal, source CIA factbook 2009
Most of Senegal has a typically tropical climate, but the northern regions lie in the Sahel. Senegal has a varied underlying Geology which gives rise to a variety of different soil types, however many are fragile and prone to erosion. Rainfall in Senegal, as in all of W. Africa, is controlled by the movement of the Inter-tropical Convergence Zone (ITCZ) and has one wet season between July and September. There is a strong north-south gradient in total rainfall with of just 300mm/year in the desert areas of the north but 1200mm/year in the forested areas of the south (MOE 2006). Rainfall is highly variable both at the inter-annually and on inter-decadal scales. Average annual temperature for Senegal was 27.8°C for the period 1960-1990, with monthly averages in the hottest seasons of up to 35°C.
Mean annual temperature in Senegal has increased by 0.9°C since 1960, an average rate of 0.20°C per decade and the rate of increase has been most rapid in OND, at 0.29°C per decade (McSweeney et al 2008). Like other countries in the Sahel Senegal experienced decreasing rainfall during the 1970s and 1980s which caused severe drought and water shortages, although there has been some amelioration of rainfall since 1990 (MOE 2006). McSweeney et al (2008) report that for southern Senegal there has been a statistically significant decrease in wet season rainfall between 1960 and 2006. River run-off has also decreased in recent decades (MOE 2006).
Drought and floods are the major climatic hazards in Senegal, Floods occur more frequently than droughts, but droughts have more severe consequences and affect many more people per event. That is not to say that floods are not severe events, as large floods in 1998 affected 300,000 people (CRED 2008). See Appendix 1 for numbers affected by floods and droughts in Senegal.
Climate Change Projections
Rainfall anomolies for Tambacounda for 2046-2065, source Climate Change Explorer
McSweeney et al (2008), using a range of models, find that the mean annual temperature is projected to increase by 1.1 to 3.1°C by the 2060s, and 1.7 to 4.9°C by the 2090s, which is consistent with IPCC projections for W. Africa of an increase of 1.8C-4.7C for 2081-2100 . It is also consistent with downscaled results from 8 climate models for various stations in Senegal, which give increases in average monthly temperatures of 1.5-4°C for 2046-2065 . The projected rate of warming is faster in the interior regions of Senegal than in those areas closer to the coast. There will be an increase in the number of ‘hot’ days, nights and seasons when compared to current climate, and a decrease in cold days and nights.
Projections of mean annual rainfall averaged over the country from different models in the ensemble project a wide range of changes in precipitation for Senegal, from -41 to +48% by the 2090s but more models show decreases, particularly in the wet season It is difficult to draw robust conclusions of changes in precipitation, however it is likely that whether there is an increase or a decrease a greater proportion of precipitation will occur in heavy rainfall events. Given the range of changes in the projections for Senegal, it is important to incorporate scenarios of both increases and decreases in precipitation in planning for future change. An illustration of the range of projected changes for the station of Tambacounda in the interior of Senegal is given in the figure above.
Agriculture in Senegal is highly dependent on rainfall and favourable climatic conditions, and this makes it vulnerable to both current climatic variability and future climate change. The increase in temperatures and evapo-transpiration will increase crop water requirements and may lead to decreased yields (World Bank 2008). The expected increase in inter-annual variability, and the likely increase in drought conditions may require to shift to cultivars that are better adapted to withstand dry conditions. Any increase in precipitation would ameliorate the situation, however, given the uncertainties in the projections, the increase in evapo-transpiration and the increase in population, it is safer to plan for reduced availability of water.
Sea-level could rise by up to 1m by the end of the century (Rahmstoff 2007), and this would put at least 110,000 people, mostly in the south of Senegal in the Cape Verde region, at risk of coastal flooding (World Bank 2008). Some studies, however, put the number of people at risk much higher (AIACC 2002). The increase in heavy rainfall events is likely to increase the incidence of floods. Possible health impacts of climate change for Senegal include an increase in water-borne diseases such as cholera in the after-math of floods, and an increase in heat-related mortality.
- UNDP Climate Change Country Profiles Senegal. C. McSweeney, M. New, and G. Lizcano
- Case Study: Gender, Human Security and Climate Change in Senegal. Yacine Diagne Gueye of ENDA. This is a chapter of WEDO’s study, Gender, Climate Change and Human Security, commissioned by the Greek chairmanship (2007-2008) of the Human Security Network.
- EM-DAT: The OFDA/CRED International Disaster Database. www.emdat.be – UniversitÃ© Catholique de Louvain – Brussels – Belgium.
- MOE (2006) Programme d’Action National pour l’Adaptation aux Changements Climatiques au Senegal.
- Rahmstorf, S. 2007 A semi-empirical approach to projecting future sea-level rise. Science 315: 368-370.
- World Bank (2008) Senegal: Climate Risk Factsheet. Draft.
Author: Ruth Butterfield
This work has been funded by the World Bank Group