Author: Julia Tomalka

Over the last decades, Niger has experienced strong seasonal and annual variation in precipitation as well as recurring droughts, all of which present major constraints to agricultural production. The country was hit by recurring droughts between 1950 and 1980 as precipitation amounts decreased during that time [18]. Although annual precipitation sums recovered afterwards, they remain below the national average of the past century [18]. Further droughts were registered in 2005, 2008, 2010 and 2012 [19]. The 2012 drought affected a total of 5.4 million people in Niger, 1.3 million of whom faced serious food insecurity and depended on humanitarian aid [20]. Extreme droughts tend to have a cascading effect: First, lack of water reduces crop yields, which increases the risk of food insecurity for people and their livestock and in turn limits their capacity to cope with future droughts [21]. Transhumance used to be an effective way to deal with variations in precipitation amounts and droughts in Niger, but people’s reliance on this type of pastoralism has been challenged by increasingly unpredictable precipitation patterns and, consequently, a lack of good pastures and water [22]. Additional stressors include increasing competition for natural resources (partly due to population growth), depletion of livestock, and intercommunal and cross-border conflicts, making this mode of living less profitable and sometimes even dangerous [22].

Per capita water availability

Current projections of water availability in Niger display high uncertainty under both GHG emissions scenarios. Assuming a constant population level, multi-model median projections suggest almost no change in per capita water availability over Niger by the end of the century under either RCP (Figure 8A). Yet, when accounting for population growth according to SSP2 projections⁴, per capita water availability for Niger is projected to decline by 85 % by 2080 relative to the year 2000 under both scenarios (Figure 8B). While this decline is primarily driven by population growth rather than climate change, it highlights the urgency to invest in water saving measures and technologies for future water consumption.

Spatial distribution of water availability

Projections of future water availability from precipitation vary depending on the region and scenario (Figure 9). In line with precipitation projections, water availability is projected to increase in most parts of the country under both RCPs. However, in most cases, model agreement on these increases is low towards the end of the century.

4 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.

References

[18] USAID, “A Climate Trend Analysis of Niger,” Washington, D.C., 2012.
[19] USAID, “Climate Change Risk Profile: West Africa Sahel,” Washington, D.C., 2017.
[20] OCHA, “Niger: 5.4 Million People Are Food Insecure,” Niamey, Niger, 2012.
[21] S. Traore and T. Owiyo, “Dirty Droughts Causing Loss and Damage in Northern Burkina Faso,” Int. J. Glob. Warm., vol. 5, no. 4, pp. 498–513, 2013.
[22] UNOWAS, “Pastoralism and Security in West Africa and the Sahel,” n.p., 2018.

Temperature

In response to increasing greenhouse gas (GHG) concentrations, air temperature over Niger is projected to rise by 2.0 to 4.6 °C (very likely range) by 2080 relative to the year 1876, depending on the future GHG emissions scenario (Figure 2). Compared to pre-industrial levels, median climate model temperature increases over Niger amount to approximately 2.1 °C in 2030, 2.5 °C in 2050 and 2.6 °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 2.1 °C in 2030, 2.7 °C in 2050 and 3.7 °C in 2080.

Very hot days

In line with rising mean annual temperatures, the annual number of very hot days (days with daily maximum temperature above 35 °C) is projected to rise substantially and with high certainty, in particular over south-western Niger (Figure 3). Under the medium / high emissions scenario RCP6.0, the multi-model median, averaged over the whole country, projects 16 more very hot days per year in 2030 than in 2000, 27 more in 2050 and 40 more in 2080. In some parts, especially in south-western Niger, this amounts to about 300 days per year by 2080.

Precipitation

Future projections of precipitation are less certain than projections of temperature change due to high natural year-to-year variability (Figure 4). Out of the four climate models underlying this analysis, one model projects almost no change in mean annual precipitation over Niger, one projects a decline and the other two models project an increase. Under RCP2.6, median model projections show a precipitation increase of 29 mm per year by 2080, while median model projections for RCP6.0 show a lower annual increase of 19 mm by 2080 compared to year 2000. The projected absolute changes in mean annual precipitation show high regional variations.

Heavy precipitation events

In response to global warming, heavy precipitation events are expected to become more intense in many parts of the world due to the increased water vapour holding capacity of a warmer atmosphere. At the same time, the number of days with heavy precipitation events is expected to increase. This tendency is also found in climate projections for Niger (Figure 5), with climate models projecting an increase in the number of days with heavy precipitation events, from 8 days per year in 2000 to 10 and 9 days per year in 2080 under RCP2.6 and RCP6.0, respectively.

Soil moisture

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 temperatures translate to higher potential evapotranspiration. Annual mean top 1-m soil moisture projections for Niger show almost no change under either RCP by 2080 compared to the year 2000 (Figure 6). However, looking at the different models underlying this analysis, there is large year-to-year variability and modelling uncertainty, with some models projecting an increase and others projecting a decrease in soil moisture. Hence, a clear trend cannot be identified.

Potential evapotranspiration

Potential evapotranspiration is the amount of water that would be evaporated and transpired if sufficient water was available at and below land surface. Since warmer air can hold more water vapour, it is expected that global warming will increase potential evapotranspiration in most regions of the world. In line with this expectation, hydrological projections for Niger indicate a stronger and more continuous rise of potential evapotranspiration under RCP6.0 than under RCP2.6 (Figure 7). Under RCP6.0, potential evapotranspiration is projected to increase by 2.2 % in 2030, 2.9 % in 2050 and 5.4 % in 2080 compared to year 2000 levels.

3 Changes are expressed relative to year 1876 temperature levels using the multi-model median temperature change from 1876 to 2000 as a proxy for the observed historical warming over that time period.