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.
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 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 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.