Climate Change and Rainfall: Part II

My previous blog explored the impacts of climate change in rainfall in terms of droughts, and more specifically in West Africa and the Sahelian region. This blog continues to explore the impacts of climate change in Africa but in terms of floods. The first thing that comes to my mind when I associate climate change with rainfall in Africa are the ideas of drought and famine, thus ideas concerning extreme rainfall and increased flood extent, I find, is very intriguing. In this blog, I want to look at floods associated with climate change and the impacts.

The dominant projections of climate change impacts on rainfall in terms of extreme rainfall and flooding events is that rainfall is more likely to become highly variable in East Africa, extreme rainfall events will become more frequent and thus result in more flooding (IPCC, 2007). Studies such as Webster et al. (1999) and Hastenrath et al. (2007) have found that in fact, East Africa has experienced both extreme rainfall as well as a lack of rainfall in the region. This anomalous extreme rainfall results in more flood events, and the frequency of flood events has increased in recent years. Shongwe et al. (2009) analysis of the International Emergency Disaster Database shows that almost 7 events per year of reported disasters, which was related to increased flooding, had occurred from 2000 to 2006. The impacts of these disasters affects economic development, poverty reduction and the well-being of an average of two million people per year (Shongwe et al., 2011). Shongwe et al. (2011) notes that the predicted impacts of global climate models are already occurring now, much sooner than anticipated. And so, the impacts of flood risk need to be analysed, and management of flooding regimes must be properly accounted for. Just because there is an expected increase in East Africa does not mean that this is necessarily a good thing.

The coastal city of Mombasa is located in Kenya and currently experiences frequent floods on a near-annual basis, however the October 2006 flood was one flood that Mombasa did not usually experience. This flood was induced by extreme rainfall which saw the destruction of important infrastructure, such as collapsed and flooded roads which can be seen in the image below, and more than 60,000 people was affected by the flood (Awuor et al., 2008). The impacts of this large flooding event worsened the social and economic conditions of the city due to the major economic losses associated with infrastructure damages, as well as the damages to fishing vessels. A large majority of Kenya’s coastal population is concentrated in Mombasa – this increased the risk of the spread of cholera (Awuor et al., 2008). The city was notified of a cholera alert whereby thirteen cases were found positive for cholera and an addition of two deaths by the 11 November 2006 (OCHA, 2006). Moreover, between 15^th and 17^th October, high rainfall levels of 110mm resulted in landslides which saw the death of five children.
The impacts of flooding are very severe in the short run in that homes are almost instantaneously destroyed, many people are displaced and the death rates of populations are widespread and the causes of these deaths range from drowning, debris or from water-borne diseases like cholera. These impacts only proves to show that flood management in vulnerable places is integral in a warming world.

 Image 1 (Left) and 2 (Right) 

There is no doubt that the increases of the number of floods in magnitude and frequency are causing huge damages to infrastructure, economic performance and livelihoods. However, some argue that the damage and extent of flood events is more than just the increased intensity and magnitude of floods as a result of climate change in recent years. Studies such as Baldassarre et al. (2010) concluded that at continental and site specific scales across Africa, the impact of climate change in this observed increase in flood damages is negligible. Instead, Baldassarre et al. (2010) attribute the increased damages of floods to higher rates of urbanisation in the last decade. They found that an increase in urban population by magnitude of 1 also saw the increase of fatalities caused by floods by a magnitude of 1. Many studies (Hardoy et al., 2001; Douglas et al., 2008; Jonkman, 2005) concluded that the increased potential of flood risk with severe and irreversible consequences is a result of intensive, rapid and unplanned urbanisation in the number of people living in floodplain areas (Balassarre et al., 2010). For example, the growth of the capital city of Lusaka in Zambia is prone to flooding, thus this growing city is expected to have higher risks to flooding (Nchito, 2007).

Concluding Thoughts:

It is very important to not take these projections of increased flood frequency and magnitude lightly, given that they are currently happening now and not in some far distant future. Proper flood management is required to minimise the impacts of these floods induced by climate change. However, as many studies found, it is difficult to isolate and differentiate the increased flood damages as a result of climate change only. Other human factors showed to account for a large part of this increasing damage, even in a globally warming world. Even though climate change may induce frequent floods, climate change should not be seen as the only cause of the increased impacts of floods in many African towns and cities. Overall, compared to droughts, the impacts of floods on many people can be minimised with the proper management of drainage systems and the construction of towns in a rapidly urbanisation, as well as working in tandem with monitoring rainfall patterns and thus predicting then floods are likely to occur as a result of intense rainfall periods. 

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. 

Variability in Africa's Physical Environment and Climate Change Impacts

Diverse Africa 

Aside from Africa’s pretty green scenery and a wide array of exotic animals, Africa is highly diverse and variable across space and time in a number of physical attributes such as biomes, precipitation patterns, topography and groundwater resources. The Hadley Cell of the atmospheric circulation over Africa results in a desert type biome in the north and south, and a tropical biome in the centre of Africa (Figure 1) due to high pressures at higher latitudes of 30°N and 30°S, and low pressure near the equator which facilitates high levels of rainfall in the tropics (Figure 2). African climate is largely determined by the interaction of three large-scale climate systems, the ITCZ, El Nino-Southern Oscillation and annual variability of Monsoon systems (Conway, 2009). The ITCZ has an extremely important role in distributing rainfall temporally and spatially over Africa. Elevation levels vary across the continent where there is low elevation in the north-east and high elevation in the south-west (Figure 3). Groundwater resources are underlain by different geological rock types and thus affecting different productivity levels (Figure 4). It is the complexity of Africa’s physical environment that should be carefully considered when discussing the impacts of climate change. 

                   Figure  1. Biomes of Africa (UNEP)    Figure 2. Precipitation patterns of Africa (UNEP)

                        Figure 3. Elevation of Africa      Figure 4. Geology of Africa (MacDonald, et al., 2012)

What is climate change?

The IPCC explains that climate change is a result of anthropogenic influences on natural climate systems and thus forcing them to change (IPCC, 2014). A major cause for climate change is due to increases in anthropogenic carbon dioxide emissions during the industrial era of the mid-20^th century and since then the subsequent economic and population growth (IPCC, 2014). Brian Kahn (2016) reports that September 2016 is a milestone in the world’s climate whereby carbon dioxide levels have surpassed the ‘symbolic’ mark of 400 ppm. The IPCC’s Fifth Assessment Report explains that we can expect more variable rainfall patterns and temperatures across Africa (Niang et al., 2014), and thus surpassing the 400ppm mark can only make these patterns more variable than ever. In a world where governments and international organisations have finally come together to tackle climate change, it just clearly shows that our current methods appear ineffective and more work is required when facing this challenge. 

Brief Overview of the Impacts of Climate Change on Africa

• Increased frequency in extreme rainfall (New et al., 2006) – IPCC (2014) for example, explains that southern Africa is experiencing increases in extreme rainfall and New et al. (2006) has shown statistically significant relationships between extreme precipitation and total precipitation whereby increases in extreme precipitation and decreases in total precipitation show that average intense rainfall is concentrated on extreme rainfall days in southern and western Africa.
• Increased frequency and intensity of droughts and floods in some regions – It is more likely that the southern and northern most parts of Africa will become hotter and drier where temperatures are projected to increase by 4°C and rainfall levels are expected to fall by 10-20% (IPCC, 2007). The IPCC AR5 suggests that temperature across Africa is likely to rise more quickly than other land areas and this is most pronounced in arid areas.
• A decrease in perennial stream or river drainage density (de Wit & Stankiewicz, 2006) – Regions receiving more than an average of 1000mm of rainfall per year and experiencing a 10% in precipitation will see a decrease in drainage by at least 17% (Figure 5). Areas with 500mm of rainfall would see a drop of 50% in surface drainage with a 10% decrease in precipitation (de Wit & Stankiewicz, 2006). Central and eastern Africa is expected to see increases in precipitation whereas precipitation in northern and southern most areas Africa is expected to decrease. 

Figure 5. Drainage density and rainfall (de Witz & Stankiewicz, 2006)

• A reduction in agricultural crop yields – General consensus of climate change impacts on agriculture shows that rain-fed crop yields are expected to fall by up to 50% by 2020 in many African countries where small scale farmers are expected to be most affected (IPCC, 2014). Roudier et al. (2011) predicts that Sudano-Sahelian countries in north-western Africa is likely to be more affected (median yield loss of –18%) than Guinean countries in south-western Africa (–13%). However, Roudier et al. (2011) also found that higher carbon fertilisation processes have the potential to improve yields for C3 (e.g. soybean) and C4 (e.g. staple crops like maize) crops. In East Africa, Thorton et al. (2009) predicted that maize yields and bean yields are likely to increase in the east African highlands such as the Kenyan and Ethiopian highlands. 

The impacts of climate change are world-wide but the same cannot be said for Africa; it is unlikely that there will be a wide African-scale effect of climate change. Instead it is more likely that climate change effects will vary within different locations of Africa due to its large landmass and heterogeneous physical and environmental features (Collier et al., 2008).

Concluding thoughts:

Africa consists of highly diverse and variable physical attributes, such as rainfall patterns, temperature, land surface geology, and elevation. Thus we should not assume that the impacts of climate change in Africa is simply homogenous on a wide continental scale, instead the impacts of climate change are regionally localised to the environmental conditions of that area. Impacts on the hydrological cycle include extreme rainfall patterns, overall decreased rainfall levels, flooding, and droughts are likely to occur unevenly across Africa.

Although the use of the term impact should be carefully considered – the impact of climate change on the hydrological climate is negative, however climate change impacts also appear positive in other areas such as carbon fertilisation processes.
Thus this blog will continue to explore the impacts of climate change on water resources and systems in Africa, and thus the impacts on people’s well-being and livelihood in Africa. 

Environmental Change and Water in Africa: An Introduction

I will be focusing on the influence of environmental change, namely climate change, on water resources and availability in Africa. Water is an incredibly important resource that is used in a variety of ways ranging from having a shower to washing your car, making and dyeing the colour of your clothes in industries and large scale agricultural practises to feed the people of the world. 

Water resources in Africa is highly variable across space and time, and so the reality of climate change will significantly influence the hydrological cycle. Impacts include changes in rainfall frequency and distribution, water supply and quality. 

Thus this blog will explore how the influence of climate change on water resources impacts people, agriculture, industries and economies through the discussion of academic articles, new articles and videos.