CMIP6-Based Temperature and Precipitation Projections under SSP Scenarios in the Data-Scarce Oti River Basin, West Africa: Bias Correction, Future Trends, and its Implications for Water Resources and Agriculture.

The Oti River Basin is among the most climate-vulnerable transboundary basins in West Africa, where limited hydro-meteorological observations constrain effective climate adaptation planning. This study assessed future precipitation and temperature changes using an ensemble of ten CMIP6 Global Climate Models under four Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5). Climate projections were analyzed for the 2020s, 2050s, and 2070s relative to historical observations (1960–2015) and reanalysis datasets (1981–2020). To improve model reliability, quantile mapping bias correction was applied using CMhyd, with ERA5 temperature and CHIRPS precipitation data as reference datasets. Bias correction substantially enhanced model performance, achieving R 2 values of 0.80–1.00 for temperature and 0.82–0.99 for precipitation. Future projections indicate a basin-wide decline in annual precipitation, with reductions reaching approximately 1050 mm yr -1 under SSP5-8.5 by the late century. Simultaneously, maximum and minimum temperatures are projected to increase markedly, with Tmax reaching 35–40°C and Tmin 24–29°C under high-emission scenarios. Spatially, the southern basin is expected to experience the most severe drying, while warming is projected across the entire basin. These climatic changes are likely to intensify drought occurrence, heat stress, and water scarcity, posing significant risks to agricultural productivity, water security, and ecosystem resilience. The findings provide critical evidence for climate adaptation planning, emphasizing the need for climate-resilient agriculture, improved water governance, and strengthened hydro-meteorological monitoring. The study contributes valuable scientific information to support national adaptation strategies, transboundary water management, and long-term climate action (SDG 13) in data-scarce regions.