Assessing the reliability and uncertainties of projected changes in precipitation and temperature in Coupled Model Intercomparison Project phase 5 models over the Lake Chad basin

摘要

Lake Chad lost more than 80% of its surface area over the past decades as a result of environmental change and climate variability. It is not yet known how climate change will affect water resources availability in the basin over the coming decades. In this study, the reliability ensemble averaging (REA) technique was used to evaluate the performance of Coupled Model Intercomparison Project phase 5 (CMIP5) models in simulating present-day precipitation and temperature (1980-2005), and to quantify the uncertainties in future projections (2050-2075) under two representative concentration pathways (RCPs) in the Lake Chad basin (LCB). Analyses were carried out at both annual and seasonal timescales. Overall, the CMIP5 models simulated precipitation better than temperature in the study area. Although the models were able to simulate the annual precipitation cycle in the basin, most models overestimated precipitation during the dry season and underestimated it during the monsoon season. Future annual basin precipitation is projected to increase by 2.5 and 5%, respectively, under RCP4.5 and RCP8.5 scenario by the middle of the century by most of the models and most of the model projections are within the REA uncertainty range. Despite the increase in projected annual precipitation in the basin, most models project a decrease in monsoon precipitation under both RCPs. Although the uncertainty range for future precipitation projections for most models lie within the range of natural climate variability, additional analysis is needed for results to be useful for any future planning in the study area.