Ghana: Improved crop varieties

Smallholder farmers in the global South mostly use traditional crop varieties, which can be vulnerable to climate impacts such as droughts, floods or also diseases. In order to improve the resilience of crops to climatic shocks and to raise yields, improved crop varieties are bred from traditional varieties. The process of breeding is lengthy and costly, but once better varieties are released and used, they can substantially improve agricultural yields and resilience, depending on their specific characteristics. As such, breeding improved varieties is an institution-led approach, since it requires resources and time, which smallholder farmers most often do not have.

Improved crop varieties can offer a number of interesting development co-benefits, especially linked to increased agricultural production and income. However, they are expensive to develop:  a multitude of factors will determine prices of the seeds, such as demand, scale of adoption, and – for farmers – potential government subsidies

A number of improved crop varieties already exist or are being developed in Ghana, for instance for maize, rice, cassava and cocoa, with sought-after properties being drought resistance, flood resistance and achievement of high yields. Maize appears to be the focus of breeding efforts in Ghana, as several publications (e.g. Alhassan, Salifu & Adebanji, 2016; Danso-Abbeam et al., 2017) and the number of active breeders for maize (10 out of 26) confirm (Mabaya et al., 2017).

An analysis conducted using the biophysical crop model APSIM shows that improved maize varieties indeed hold large potential for increasing yields under climate change (Figure 3). However, the size of the effect and sometimes even direction depends on the location, with the impact in different districts in Ghana differing considerably. Compared to no adaptation and other agronomic adaptation measures such as applying manure or delaying the sowing date, a carefully selected improved variety may indeed have a larger impact on increasing maize yields.

Table 1: Impact of agronomic adaptation measures on maize yield under climate change for three districts in Ghana (average yield projection for 2050 compared to 2006 baseline).

Another analysis conducted with machine-learning based crop suitability models shows how generally the effect of agronomic adaptation strategies varies considerably across crops. While maize and cassava appear to benefit from many agronomic adaptation strategies under climate change, for sorghum this is much more the case under the high-emission climate scenario (RCP8.5) and for groundnut, none of the adaptation strategies proposed has a positive effect.

Figure 3: Projected effects of different adaptation options on crop suitability for cassava, groundnut, maize and sorghum under RCP2.6 and RCP8.5. The adaptation options analysed are: a two-week shift in the growing season (beige), a four-week shift in the growing season (red), increasing soil organic carbon by 10% (brown), a combination of shifting the growing season by two weeks and increasing soil organic carbon by 10% (grey) and a combination of shifting the growing season by four weeks and enhancing soil organic carbon by 10% (mint).

Agronomic adaptation strategies and the use of improved seeds should thus be carefully evaluated for each specific region, crop and climate impact scenario. Nonetheless, improved crop varieties are seen as a transformative tool for buffering climate impacts in Ghanaian agriculture. Breeding is costly and time intensive, but where improved varieties already exist, they can contribute importantly to a higher agricultural output.


  • Alhassan, A., Salifu, H., & Adebanji, A. O., (2016). Discriminant analysis of farmers’ adoption of improved maize varieties in Wa Municipality, Upper West Region of Ghana. SpringerPlus, 5(1).
  • Danso-Abbeam, G., Bosiako, J. A., Ehiakpor, D. S., & Mabe, F. N., (2017). Adoption of improved maize variety among farm households in the northern region of Ghana. Cogent Economics and Finance, 5(1), 1–14.
  • Mabaya, E., Adzivor, S. Y., Wobil, J., & Mugoya, M., (2017). Ghana Brief 2017 – The African Seed Access Index, (December).

Ghana: Rainwater harvesting

Rainwater harvesting (RWH) allows storing irrigation water for critical times in the growing period of otherwise rain-fed crops. It is also a promising practice for reducing costs for irrigation uptake as its installation is considerably cheaper than building groundwater irrigation infrastructure.

In Ghana, limited evidence on the use and potential of RWH for small-scale irrigation systems exists. Even though Ghana has abundant water resources for irrigation, its uptake is very low. RWH can provide a cost-efficient alternative to irrigation installment and is notably a strategy with usage potential at different scales. It is particularly well suited to be coupled with farm-level horticulture production, either for additional income from vegetable sales or satisfying changing demands in household consumption (for Sub-Saharan Africa as a whole, see e.g. OECD & FAO, 2016). This could also yield nutritional and thus health benefits, with vegetables enriching otherwise staple-based diets in Ghana. A combination with conservation agriculture techniques can be particularly useful, with further improvements in soil water storage capacity enhancing the water use efficiency of RWH.

In addition, RWH has the potential to deliver gender co-benefits. Since it is usually women who are in charge of fetching water and who engage in backyard vegetable farming, collecting rainwater could save women time, making time for other activities and enabling additional farming activities.

Rainwater harvesting and small-scale irrigation are a good alternative for action at smallholder level, with simple installation techniques proving less difficult to implement, maintain and refinance as compared to large-scale irrigation systems.

Thus, RWH is a promising adaptation strategy meeting local interest in Ghana. It can be implemented by farmers autonomously and decrease dependency on precipitation.


  • OECD/FAO, (2016). Agriculture in Sub-Saharan Africa: Prospects and challenges for the next decade, in OECD-FAO Agricultural Outlook 2016-2025, OECD Publishing, Paris.

Ghana: Irrigation

In areas short of precipitation, irrigation can be a key strategy to enable plant growth and increase yields. Water can be drawn from different sources, such as groundwater, surface water and in some countries even desalinated seawater, to enable a better growth of plants. Irrigation schemes at smaller scale can be initiated and implemented by farmers themselves, but for larger irrigation installations, technical agencies and extension officers play an important role.

As of yet, irrigation is not widely spread in Ghana, with only an estimated 1.6% of the area with a respective potential actually being irrigated (Mendes, Paglietti & Jackson, 2014), mostly for rice and horticulture cultivation (Namara et al., 2011). This limited uptake implies that further installation of irrigation schemes is possible and could increase Ghana’s agricultural production. However, this may incur high costs and technically challenging installation and maintenance. As a climate change adaptation strategy, the case for irrigation depends on the climate scenario, with the North of Ghana projected to see less rainfall under future climate change. However, as a measure to intensify agricultural production and enable multiple harvests, irrigation can also be considered useful today, where water is available for agricultural use.

Figure 2 shows the net value of maize production in the whole of Ghana under different irrigation scenarios, reflecting the varying costs that different irrigation techniques and installations incur. As can be seen from the comparison with the baseline scenario and the scenario under climate change, not all irrigation scenarios are able to offset the losses projected under climate change.

Figure 2: Net value of maize production in Ghana under different irrigation scenarios (in million USD), compared to no adaptation and no climate change.

In sum, while irrigation has the potential to increase agricultural production in Ghana, it is also a costly strategy, often requiring institutional support for implementation and maintenance.


  • Mendes, D.M, Paglietti, L. & Jackson, D., (2014). Ghana: Irrigation market brief. Food and Agri-culture Organization of the United Nations. Rome.
  • Namara, R., Horowitz, L., Nyamadi, B. & Barry, B., (2011). Irrigation Development in Ghana: Past experiences, emerging opportunities, and future directions, International Food Policy Research Institute, GSSP Working Paper No. 27, Ghana Strategy Support Program, Accra.

Ghana: Human health

Climate change threatens the health and sanitation sector through more frequent incidences of heatwaves, floods, droughts and dry winds [32]. Climate change impacts on health can be direct, e.g. via increasing exposure to heatwaves or floods, or indirect, e.g. via more frequent incidences of vector-borne diseases, such as malaria, as well as via increasing food insecurity or malnutrition.

Heatwave exposure and mortality

Rising temperatures will result in more frequent heatwaves in Ghana, which will increase heat-related mortality. Under RCP6.0, the population affected by at least one heatwave per year is projected to rise from 5 % in 2000 to 19 % in 2080 (Figure 17). Furthermore, under RCP6.0, heat-related mortality will likely increase from about 1 to about 5 deaths per 100 000 people per year, which translates to an increase by a factor of more than five towards the end of the century compared to year 2000 levels, provided that no adaptation to hotter conditions will take place (Figure 18). Under RCP2.6, heat-related mortality is projected to increase to about 2 deaths per 100 000 people per year.

Figure 18: Projections of at least once per year exposure of population to heatwaves for Ghana for different GHG emissions scenarios.
Figure 19: Projections of heat-related mortality for Ghana for different GHG emissions scenarios assuming no adaption to increased heat.

Among the key health challenges in Ghana are also communicable diseases, such as malaria, tuberculosis, and HIV, maternal and children’s health as well as malnutrition, many of which are expected to become increasingly severe under climate change. Studies show that Malaria, diarrhea, and Cerebro Spinal Meningitis are being aggravated by impacts of climate change in Ghana [33].


[32] A. Haines, R. S. Kovats, D. Campbell-Lendrum, and C. Corvalan, “Climate change and human health: Impacts, vulnerability and public health,” Public Health, vol. 120, no. 7, pp. 585–596, Jul. 2006.
[33] D. B. K. Dovie, M. Dzodzomenyo, and O. A. Ogunseitan, “Sensitivity of health sector indicators’ response to climate change in Ghana,” Sci. Total Environ., vol. 574, pp. 837–846, Jan. 2017.

Ghana: Ecosystems

Climate change is anticipated to have a significant influence on the ecology and distribution of tropical ecosystems, though the magnitude, rate and direction of these changes are uncertain [29]. Under rising temperatures, increased frequency and intensity of droughts and shorter growing periods, wetlands and riverine systems become at risk of being converted to other ecosystems with plants being succeeded and animals losing habitats. Increased temperatures and droughts can also affect succession in forest systems while concurrently increasing the risk of invasive species, all of which affect the ecosystems. In addition to these climate drivers, reduced agricultural productivity and population growth might motivate further agricultural expansion resulting in increased deforestation, forest degradation and in return in increased forest fires, all of which will impact animal and plant biodiversity [30]. While ecosystems in the northern areas of Ghana are expected to be particularly affected given the higher expected temperature increase and mounting pressure from human land use, the challenges are prevalent throughout the entire country.

Species richness

Model projections of species richness (including amphibians, birds, and mammals) and tree cover for Ghana are shown in Figure 16 and 17, respectively. The volatility in species richness between 2030 and 2050 under RCP6.0 suggest a high sensitivity of species survival and population recovery to natural climate variability. Overall, however, model results indicate a slightly positive long-term impact of climate change on species richness under both RCPs (Figure 15), with the majority of models (at least 75 %) agreeing on this trend.

Figure 16: Projections of the aggregate number of amphibian, bird, and mammal species for Ghana for different GHG emissions scenarios.

Tree cover

With regards to tree cover shifts, model results are highly uncertain. Until mid-century, tree cover is projected to not change significantly in most parts of Ghana. Towards the end of the century, the average model projects slight decreases of tree cover under RCP2.6 and slight increases under RCP6.0, yet model agreement about these trends is low in most parts of the country (Figure 16).

Although these results paint an overall positive picture for climate change impacts on ecosystems and biodiversity, it is important to keep in mind that the model projections exclude any impacts on biodiversity loss from human activities such as land use, which have been responsible for significant losses of global biodiversity in the past, and are expected to remain the main driver of biodiversity loss in the future [31].

[28] T. M. Shanahan et al., “CO2 and fire influence tropical ecosystem stability in response to climate change,” Sci. Rep., vol. 6, no. 1, p. 29587, Jul. 2016.
[29] S. Agyemang, M. Muller, and V. R. Barnes, “Fire in Ghana’s dry forest: Causes, frequency, effects and management interventions,” in Proceedings of the large wildland fires conference, 2014, pp. 15–21.
[30] IPBES, “Global Assessment Report on Biodiversity and Ecosystem Services,” Bonn, 2019.

Ghana: Infrastructure

Extreme weather events have been the cause of major damage to the infrastructure sector in Ghana in the past. A study by Twerefou et al. [25] from 2014, for example, states that within one year, 1016 km of roads were destroyed, 13 bridges collapsed and 442 sewers damaged in the northern region of Ghana in 2007 alone through climate-related events. In general, high temperature can cause roads to develop cracks, while high precipitation rates may create potholes or deepen existing ones. [26]. Transport infrastructure is very vulnerable to extreme weather events and yet very important for social, economic and agricultural livelihoods. Roads allow communities to trade their goods and access healthcare, education, credit, as well as other services, especially in rural and remote areas of Ghana.

Storms, extreme rainfall and floods can also have devastating effects on economic production sites as well as settlements, especially in areas where large populations reside, such as Accra, Kumasi and Tamale. Informal settlements are particularly vulnerable to these events, as structures are generally weak and dwellers have low adaptive capacity to respond to disruptive events. Hydropower generation plants are affected by both droughts and floods, whereas sea level rise is already beginning to erode coastal roads [27]. Overall, climate change will make the life span of infrastructure shorter than planned while maintenance costs will increase significantly to keep them functioning [27], [28].

Figure 13: Projections of at least once per year exposure of major roads to river floods for Ghana for different GHG emissions scenarios.
Figure 14: Projections of at least once per year exposure of urban land area to river floods for Ghana for different GHG emissions scenarios.

Under climate change, extreme weather events are likely to become more frequent, and temperatures are projected to rise. Accordingly, the risk for infrastructure damage in the country is likely to increase. However, precise predictions of the location and extent of exposure are difficult to make. For example, projections of river flood events are subject to substantial modelling uncertainty, largely due to the uncertainty of future projections of precipitation amounts and their spatial distribution, affecting affecting flood occurrence (see also Figure 5). According to this analysis, flood projections show a decrease in exposure for one climate model, no change for another, a slight increase for the third and a strong increase for the fourth. Thus, no reliable estimates on river flood occurrence in the future can be made. While median model trends suggest an approximate doubling of road exposure to floods under RCP6.0 (Figure 13) from 2000 to 2080, the very likely range of model results indicates a possibility of up to a fivefold increase in road exposure to floods by 2080 (from 0.2 % of the national road network exposed in 2000 to 1.1 % in 2080). Also urban land area exposed to floods is projected to increase (Figure 14), with a very likely range of 0–0.6 % of the urban area exposed by 2080 under RCP 6.0.

Twerefou et al. [27] estimate that the future (2020-2100) cost of climate change-related damage on road infrastructure will amount to USD 473 million if no adaptation actions are taken, and USD 678.47 million if pricing in the costs for adaptation efforts in designing and constructing new road infrastructure. They estimate that the highest adaptation costs will incur in the northern region and the lowest in the greater Accra region.

Figure 15: Exposure of GDP in Ghana to heatwaves for different GHG emissions scenario.

With the impact to GDP from heatwaves projected to increase from around 5 % in 2000 to 15 % (RCP2.6) and 20 % (RCP6.0) by the end of the century, it is recommended that policy planners start identifying heat-sensitive economic production sites and activities, and integrating climate adaptation options, such as improved, solar-powered cooling systems or switching of operation times from day to night.


[25] D. Twerefou, K. Adjei-Mantey, and N. Strzepek, “The economic impact of climate change on road infrastructure in sub-Saharan Africa countries: evidence from Ghana,” 2014.
[26] M. Taylor and M. Philp, “Adapting to climate change-implications for transport infrastructure, transport systems and travel behaviour,” Road Transp. Res., vol. 19, no. 4, 2011.
[27] D. Twerefou, K. Adjei-Mantey, and N. Strzepek, “The economic impact of climate change on road infrastructure in sub-Saharan Africa countries: evidence from Ghana,” World Institute for Development Economics Research. Helsinki, Finland, 2014.

Ghana: Agriculture

Agriculture is amongst the sectors most exposed to climate change. Smallholder farmers in Ghana are increasingly challenged by the uncertainty and variability of weather that climate change causes, particularly in the northern regions of Ghana. Since crops are predominantly rainfed (as less than 1 % of the national crop area is irrigated), crop yields depend on water availability and are susceptible to drought. The impacts of climate change on the agricultural sector will be crop-specific and also site-specific with major negative impacts expected for maize in the central to northern parts of the country [24]. Yet, the high uncertainty of water availability projections (Figure 10) translates to high uncertainty in drought projections (Figure 11). According to the median over all models employed for this analysis, the national crop land area exposed to at least one drought per year will hardly change in response to global warming. However, there are models that project an increase in drought exposure. Under RCP6.0, the likely range of drought exposure of the national crop land area per year widens from 0.3–8.8 % in 2000 to 0.5–21.0 % in 2080. The very likely range widens from 0.1–25.0 % in 2000 to 0.1–53.0 % in 2080. This means that some models project more than a doubling of drought exposure over this time period, while others project no change.

Figure 11: Projections of at least once per year exposure of crop land area to drought for Ghana for different GHG emissions scenarios.

In terms of yield projections, model results indicate a clear negative yield trend for maize and millet under both RCP2.6 and RCP6.0. As a best estimate, compared to year 2000, yields averaged over the whole country are projected to decline by 9% for maize and 10% for millet by 2080 under RCP6.0, and by 4% and 5% under RCP2.6, respectively. Yields of cassava, groundnuts and field peas, on the other hand, are projected to significantly gain from climate change. Under RCP6.0, yield increases by 2080 relative to year 2000 are projected to amount to 33% for cassava, 14% for field peas, and 3% for groundnuts. A possible explanation for the positive results under RCP6.0 is that cassava, groundnuts and field peas are so-called C3 plants, which follow a different metabolic pathway than maize and millet (which are C4), and thus benefit more from the CO2 fertilization effect under higher concentration pathways. Cassava and groundnuts are also more tolerant to both low and high rainfall extremes.

Figure 12: Projections of crop yield changes for major staple crops in Ghana for different GHG emissions scenarios assuming constant land use and agricultural management, relative to the year 2000.

[24] L. Murken et al., “Climate Risk Analysis for Identifying and Weighing Adaptation Strategies in Ghana,” 2019.

Ghana: Water resources

A significant number of households (~40 %) depend on groundwater especially in the north [20], [21]. In particular after mid-century, climate change will reduce the recharge into groundwater reservoirs (aquifers), while increased requirements for agricultural water use under dry periods can lead to water scarcity. This risk is significant for closed basins such as Lake Bosomtwi, which has a small catchment [22]. In the south, sea level rise and storm surges will also increase the risk of salt water intrusion in freshwater especially in aquifers. Model results from the literature for the impacts of climate change on the Volta river basin in Ghana indicate that extreme flows will be more frequent [23], [24]. This means there is a likely increase of periods with either relatively higher or lower mean annual discharge than in the past, sometimes in consecutive years, affecting availability of fresh water for agriculture, sanitation, generation of hydropower and other economic activities.

Per capita water availability

Figure 9: Projections of water availability from rainfall per capita and year with national population held constant at year 2000 level (A) and changing according to SSP2 projections (B) for different GHG emissions scenarios, relative to the year 2000.

Current projections for water availability in Ghana display high uncertainty under both GHG emissions scenarios. Assuming a onstant population level, multi-model median projections suggest a slight decline in per capita water availability over Ghana by the end of the century under both RCP2.6 and RCP6.0 (Figure 9). Yet, when accounting for population growth according to SSP2 projections², per capita water availability for Ghana is projected to decline by about 70 % by 2080 relative to year 2000 (Figure 9, B). While this decline is not primarily driven by climate change but population growth, it highlights the urgency to invest in water saving measures and technologies for future water consumption.

Spatial distribution of water availability

Looking at the spatial distribution of future water availability projections within Ghana, it becomes evident that water saving measures will become especially important after 2050 in the north of the country (Figure 10). For all other parts of Ghana, water availability projections are too uncertain to make any such statement.

Figure 10: Water availability from precipitation (runoff) projections for Ghana for different GHG emissions scenarios.

² Shared Socio-economic Pathways (SSPs) outline a narrative of potential global futures, including estimates of broad characteristics such as country-level population, GDP, or rate of urbanisation. Five different SSPs outline future realities according to a combination of high and low future socio-economic challenges for mitigation and adaptation. SSP2 represents the “middle of the road”-pathway.


[20] P. Gyau-Boakye and S. Dapaah-Siakwan, “Groundwater as source of rural water supply in Ghana,” J. Appl. Sci. Technol., vol. 5, no. 1, pp. 77–86, 2000.
[21] E. Obubie and B. Barry, “Ghana,” in Groundwater availability and use in Sub-Saharan Africa: a review of 15 countries, P. Pavelic, M. Giordano, B. Keraita, T. Rao, and V. Ramesh, Eds. Colombo, Sri Lanka: International Water Management Institute (IWMI), 2012, p. Ch. 4, pp.43–64.
[22] B. F. Turner, L. R. Gardner, and W. E. Sharp, “The hydrology of Lake Bosumtwi, a climate-sensitive lake in Ghana, West Africa,” J. Hydrol., vol. 183, no. 3–4, pp. 243–261, Sep. 1996.
[23] K. Owusu, P. Waylen, and Y. Qiu, “Changing rainfall inputs in the Volta basin: implications for water sharing in Ghana,” GeoJournal, vol. 71, no. 4, pp. 201–210, Apr. 2008.
[24] L. Murken et al., “Climate Risk Analysis for Identifying and Weighing Adaptation Strategies in Ghana’s Agricultural Sector,” 2019.

Ghana: Post-harvest management

Effective post-harvest management is crucial to avoid food loss along the value chain. Investments in scaling technologies for improved post-harvest management have high potential for reducing crop losses, also and especially under climate change. With climate change altering growing and harvesting seasons, post-harvest management is important to cope with increased uncertainty. It is a risk-reducing strategy that lowers the vulnerability of crop production to climate impacts. Next to main staple crops such as maize and beans, post-harvest loss (PHL) of easily perishable horticulture crops could be avoided. Numerous effective and low-cost technologies exist that can prevent or reduce PHL.

Ghana’s NDC Implementation and Investment plan lists post-harvest management as a priority for adapting agriculture to climate change, with interviews confirming wide-spread interest in such strategies. A concrete post-harvest technology with promising results in the context of maize production in Ghana have been so-called PICS bags (Purdue Improved Cowpea Storage): simple and affordable yet effective hermetic storage bags originally developed for storing cowpea. Implementation of improved post-harvest management strategies can be recommended across the country as a low-hanging fruit, since better post-harvest management can increase agricultural production considerably.

Furthermore, as the economic analysis confirmed, most post-harvest management measures are rather low cost interventions, with most intervention types being “no regret” strategies because even in the absence of climate change, the improvement in crop handling will lead to lower crop losses and higher agricultural output, being economically sensible. Figure 1 shows the net value of maize production under different post-harvest management scenarios, compared to scenarios of maize production without adaptation – both with (CC) and without climate change (BAS). Except for the highest cost scenario (MAX), all other PHM scenarios do not only make up for the maize losses under climate change, but are also able to surpass maize production under the baseline scenario (without climate change and without adaptation). This shows their high economic viability.

Figure 1: Net value of maize production in Ghana with different PHM scenarios, compared to no adaptation and no climate change (in million USD).

Overall, post-harvest management strategies have considerable potential in Ghana and, being an often low-cost and no-regret strategy, can be recommended for wider implementation.

Ghana: Climate


Figure 2: Air temperature projections for Ghana for different GHG emissions scenarios, relative to the year 1876.

In response to increasing greenhouse gas (GHG) concentrations, air temperature over Ghana is projected to rise by 0.7 – 2.7°C (very likely range) by 2080 relative to year 2000, depending on the future GHG emissions scenario. Compared to 2000 levels, median climate model temperature increases over Ghana amount to approximately 0.8°C in 2030, 1.1°C in 2050, and 1.2°C in 2080 under the low emissions scenario RCP2.6. Under the medium/high emissions scenario RCP6.0, median climate model temperature increases amount to 1.0°C in 2030, 1.5°C in 2050, and 2.3°C in 2080.

Very hot days

Figure 3: Projections of the annual number of very hot days (daily maximum temperature greater than 35 °C) for Ghana for different GHG emissions scenarios.

In line with rising annual mean temperatures, the annual number of very hot days (days with daily maximum temperature greater than 35°C) is projected to rise substantially in particular over northern Ghana. Under the medium/high emission scenario RCP6.0, on average over all of Ghana, the median climate model projects 34 more very hot days per year in 2030 than in 2000, 55 more in 2050, and 94 more in 2080. In some parts, especially in the North of Ghana, this amounts to about 300 days per year by 2080.

Sea level rise

Figure 4: Sea level rise projections for the coast of Ghana for different GHG emissions scenarios, relative to the year 2000.

In response to globally increasing temperatures, the sea level off the coast of Ghana is projected to rise. Until 2050, very similar sea levels are projected under different GHG emissions scenarios. Under RCP6.0 and compared to year 2000 levels, the median climate model projects a sea level rise by 11 cm in 2030, 20 cm in 2050, and 39 cm in 2080. This threatens Ghana’s coastal communities and may cause saline intrusion in coastal waterways and groundwater reserves.


Figure 5: Annual mean precipitation projections for Ghana for different GHG emissions scenarios, relative to the year 2000.

Future projections of precipitation are substantially more uncertain than projections of temperature or sea level rise. Detecting trends in annual mean precipitation projections is complicated by large natural variability at multi-decadal time scales and considerable modelling uncertainty (Figure 5). Of the four climate models underlying this analysis, one projects a decline in annual mean precipitation over Ghana. According to the other three models, there will be no change. Therefore, our best estimate is that there will be almost no change in total precipitation per year until 2080 irrespective of the emissions scenario, yet this result is highly uncertain.

Heavy precipitation events

Figure 6: Projections of the number of days with heavy precipitation over Ghana for different GHG emissions scenarios.

In response to global warming, extreme precipitation events are expected to become more intense in many parts of the world due to the increased water vapor holding capacity of a warmer atmosphere. At the same time, the number of days with heavy precipitation is expected to increase. This tendency is also found in climate projections for Ghana, with climate models projecting a slight increase in the number of days with heavy precipitation events, from 7 days/year in 2000 to 8 days/year under RCP2.6 or 9 days/year under RCP6.0 by 2080. Central Ghana is subject to increased heavy precipitation, while for the far north, no change is projected by the multi-model mean.

Soil moisture

Figure 7: Soil moisture projections for Ghana for different GHG emissions scenarios, relative to the year 2000.

Soil moisture is an important indicator for drought conditions. In addition to soil parameters, it depends on both precipitation and evapotranspiration and therefore also on temperature as higher temperature translates to higher potential evapotranspiration. Annual mean top 1-m soil moisture projections for Ghana show a decreasing tendency. This tendency is stronger than the corresponding precipitation change projections, which reflects the influence of temperature rise on evapotranspiration.

Potential evapotranspiration

Figure 8: Potential evapotranspiration projections for Ghana for different GHG emissions scenarios, relative to the year 2000.

Potential evapotranspiration is the amount of water that would be evaporated and transpired if there were sufficient water available at and below the land surface. Since warmer air can hold more water vapor, it is expected that global warming will increase potential evapotranspiration in most regions of the world. In line with this expectation, hydrology projections for Ghana indicate a stronger rise of potential evapotranspiration under RCP6.0 than under RCP2.6. Specifically, under RCP6.0, compared to year 2000 levels, potential evapotranspiration is projected to increase by 3.2% in 2030, 4.6% in 2050, and 7.4% in 2080.