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Spatio-temporal variation in rainfall-runoff erosivity resulting from changes in rainfall characteristics due to climate change has implications for soil and water conservation in developing countries. Understanding past and future variations in rainfall-runoff erosivity and its implication, in tropical areas where there are limited continuous daily rainfall records, is important. The present study attempted to (i) quantify the nature of spatio-temporal variability of erosivity from rainfall amount using Global Circulation Models (GCMs), and (ii) evaluate the implications of changes in rainfall-runoff erosivity in the Lower Niger Basin, West Africa. The GCMs scenarios (GFDLCM3, HADCM2, MIROC5, and MPIESMLR) were statistically downscaled using the delta method for three-time slices (the 2030s, 2050s, and 2070s). World climate data was used as the current baseline climate since it is the source of the future precipitation simulation. The R factor from the Revised Soil Loss Equation (RUSLE) was used to determine erosivity, while the RUSLE model was used to ascertain the implications of changes in erosivity. Observation data (1970-2013) from 20 meteorological stations were used to validate the erosivity model. The result indicates that there is an increasing trend in the annual rainfall-runoff erosivity from the baseline climate up to the GCMs, for all the GCMs, with an average change in rainfall-runoff erosivity of about 14.1%, 19%, and 24.2% for the 2030s, 2050s, and 2070s respectively. There was a concomitant increase in soil loss of 12.2%, 19.3% and 20.6% from the baseline for the 2030s, 2050s, and 2070s respectively. Though the combined average annual rainfall and erosivity show steady increases, some of the models (GFDLCM3-2.6 and HADCM2-2.6) reveal a likely decrease in annual rainfall and erosivity for the 2070s. Higher precipitation amounts were the major drivers of increasing spatial and temporal rainfall-runoff erosivity. More studies should be performed to include other important factors that exacerbate increases in erosivity, especially future changes in land use.