In response to increasing greenhouse gas (GHG) concentrations, air temperature over Mali 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 Mali amount to approximately 2.2 °C in 2030, 2.6 °C in 2050 and 2.7 °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 2.2 °C in 2030, 2.8 °C in 2050 and 4.0 °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 dramatically and with high certainty all over Mali (Figure 3). Under the medium / high emissions scenario RCP6.0, the multi-model median, averaged over the whole country, projects 23 more very hot days per year in 2030 than in 2000, 34 more in 2050 and 59 more in 2080. In some parts, especially in central Mali, this amounts to about 300 days per year by 2080.
Models project no clear trend for precipitation, which is due to high uncertainty and natural year-to-year variability (Figure 4). Out of the four climate models underlying this analysis, one model projects an increase in mean annual precipitation over Mali, one model projects no change, while two models project a decrease under RCP6.0. Median model projections for RCP2.6 show a slight decrease of 2 mm in precipitation until 2080, while median model projections for RCP6.0 show a stronger precipitation decrease of 10 mm by 2080 compared to year 2000.
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. However, this tendency cannot be found in climate projections for Mali: Two models project a decrease, one projects no change and only one model projects an increase. Median climate model projections show a slight decrease in the number of days with heavy precipitation from 7.7 in the year 2000 to 7.5 (RCP2.6) and 7.3 (RCP6.0) by 2080 (Figure 5).
Soil moisture is an important indicator for drought conditions. In addition to soil parameters and management, 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 Mali show no change under RCP2.6 and a decrease of 3.7 % under RCP6.0 by 2080 compared to the year 2000 (Figure 6). However, there is considerable spatial variability and modelling uncertainty, as different hydrological models project different directions of change, which makes it difficult to identify a clear trend.
Potential evapotranspiration is the amount of water that would be evaporated and transpired if sufficient water was available at and below the 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 Mali indicate a stronger rise of potential evapotranspiration under RCP6.0 than under RCP2.6 (Figure 7). Under RCP6.0, potential evapotranspiration is projected to increase by 2.4 % in 2030, 3.7 % in 2050 and 7.0 % in 2080 compared to year 2000 levels.