Effects of climate change and drought attributes in Nigeria based on RCP 8.5 climate scenario

Historical observatory and future simulated datasets based on representative concentration pathway (RCP) 8.5 scenario covering from 1951 to 2100 were analysed. Four well accepted drought indices: the standardized precipitation index (SPI), standardized runoff index (SRI), reconnaissance drought index (RDI) and standardized precipitation and evapotranspiration index (SPEI) were used in drought characterization. The ensemble of the seven GCMs using RCA-4 captured some pragmatic features of the climatology of Nigeria in the historical period. The correlations between SRI and SPEI/SPI are significant. The major peaks can be divided into three drought cycles with 1–2, 2–4 and 8–16 periods (years). On a general note, there is a projection of an increase in both the frequency and intensity of drought in the five classified agroecological zones in Nigeria. Considering the output of drought characteristics as measured by SPI, future climates were predicted to be more wet when compared to the historical period as indicated in the study. In contrast, SPEI and RDI forecasted dryer climates. The prediction of SPEI and RDI must have been predicated on the influence of increasing temperature due to global warming as captured by RCP 8.5, which would in turn affect the rate of evapotranspiration. In view of drought analysis using the RCP 8.5 scenario, the frequency of severe/extreme drought will likely become more intense especially towards the end of the 21st century.