Climate Change and Rainfall: Part I

Rainfall is extremely important in Africa because most of people’s livelihoods are based on agriculture (Thorton et al., 2008). Agriculture is mainly rain-fed and hence, is highly sensitive to extreme weather conditions such as droughts, floods, intense rainfall and high temperatures (Molua, 2002).
As mentioned in the previous blog, many reports and models (IFAD, 2009; IPCC, 2007) explain that climate change is expected to have an adverse effect on rainfall patterns, and the largest impact being in Africa due to their high dependence on agriculture, harsh environments and weather conditions, and low adaptability (Dinar et al. 2008). Rainfall is expected to decrease in northern, southern and west Africa, due to increasing temperatures and evapotranspiration (IPCC, 2008). East African rainfall is expected to increase and become more variability and intense rainfall events are likely to be more frequent. Also, central Africa is expected to have more variable extreme weather events. These models and predictions are only estimations of what is ‘likely’ to happen so there are high levels of uncertainty, especially of how the impacts of climate change operate on a regional and local scale. Thus, this blog will look at the regions that are expected to experience decreases in rainfall variability and droughts.


Recent studies have observed the current trends in rainfall patterns over different regions of Africa, and most studies have found that while increases in rainfall availability have occurred in some areas, decreases in rainfall is somewhat more notable (Kotir, 2011).
Southern Africa experienced a declining trend of rainfall has occurred over the last 25 years and one of the worst droughts in Southern Africa occurred in the 1991/1992 season, where water systems and dams have failed, and emergency boreholes was set up to provide some amount of water supply (Magadza, 1994). Joubert et al. (1996) have found that the number of droughts are expected to decrease in the sub-continent of southern Africa, however when droughts do occur they’re expected to be more severe.
In West Africa, Agumagu (2016) have found that the Sahel region of West Africa experienced long term declines in precipitation during the first and last half of the 20th century. The low precipitation levels in the northern region of the Sahel is linked to climatic changes. Hulme et al. (2001) found declines of about 20–40% of rainfall in the same region of West Africa, and declines in other parts of Africa is widely variable from 5–49% since the 1960s. Overall declines in precipitation can be seen in figure 1.

Figure 1. Indices of Sahel rainfall variability. (Giannini et al., 2008)

The result of declining rainfall in the Sahel have led to many droughts, e.g. Giannini et al’s (2003) study linked the droughts to the warming of tropical oceans, and hence attributed the late 20th century drought to global warming. Biasutti & Giannini (2006) ocean-atmosphere model (CMIP3 in IPCC AR4) and Rostayn & Lohmann’s (2002) study showed that anthropogenic activities, and thus climate change, had influenced rainfall and drought conditions in Africa by modelling and linking greenhouse gases and anthropogenic sulphate aerosols to a reduction of tropical rainfall and subsequently the drying of the Sahel. However, these studies can insofar attribute the role of industrialisation and aerosol emissions on changing rainfall patterns in Africa (Giannini et al., 2008). This is because these models tend influence of other climate processes such as ENSO on African rainfall, and land-atmosphere processes or the role of biomass in temperature and rainfall controls (Hulme et al. 2001).

An interesting study by Mertz et al. (2009) attempted to analyse rural farmers’ perception of climate change in the Sahel region, and results largely show contrasting perceptions to the IPCC portrayal of the impacts of drought. The IPCC attributed negative impacts of droughts to crop failure because of low rainfall levels. Interestingly however, the main ‘negative’ impacts of droughts that was mentioned the most was excessive rainfall and strong winds, being mentioned 14 and 30 times respectively, compared to a lack of rainfall that was mentioned only eight times (Mertz et al., 2009). Clearly this shows that despite mainstream views of agriculture being affected the most due to low rainfall, other problems are more important to small scale farmers who live in Africa and experiences these conditions daily. Hence, we can interpret that farmers are more resilient to less rainfall, due to adaptive measures such as planting new cops and varieties (e.g. vegetables) or replacing horses with cattle which is cheaper to feed and the use of manure to counter agricultural problems. But these rural farmers are less resilient to e.g. strong winds that causes damage to their millets, roofs and houses which also effects their livelihoods, not just a lack of rainfall.

Concluding Thoughts:

Projections of changes in rainfall variability by reports such as the IPCC AR4 across Africa have shown to be evident in many studies whereby droughts in the Sahel or southern Africa are becoming more frequent or limited in frequency yet severe in severity. Although the results of these studies, and especially those that use models should be carefully considered because these results may exclude certain processes and relationships that is very important in rainfall processes over Africa and so one should question if the links of declining rainfall to climate change are robust. This blog focused mainly on droughts in the Sahel region of west Africa because I found the responses of farmers to the droughts in Sahel to be very interesting and it made me change my views of the needs of farmers, and not just their ‘adaptability’ to climate change. Conventional ideas of reduced agricultural yields appeared to be the most devastating impact on farmers and thus their livelihoods, and I usually submit myself to accepting this common ‘impact’ of climate change on small scale farmers. However, the contrasting opinions of these rural farmers greatly informed me of the different needs that these farmers have and not just their agricultural yields, such as their homes and infrastructure; these farmers already appear to be well equipped to droughts.