A comparative assessment of CMIP5 and CMIP6 in hydrological responses of the Yellow River Basin, China

Investigation of the role of multiple general circulation model (GCM) ensembles in obtaining comprehensive knowledge of hydrological responses across the Yellow River Basin (YRB), China, is still of substantial importance. This study evaluates the performance of the Coupled Model Intercomparison Project Phase 6 (CMIP6) models in simulating the hydrological regime in the YRB and compares the results with those from CMIP 5 (CMIP5). The comparison is performed between 21 GCMs from CMIP6 under three Shared Socioeconomic Pathway scenarios and 18 GCMs from CMIP5 under three Representative Concentration Pathway scenarios. Raw CMIP outputs are first corrected and down-scaled by the Bias Correction and Spatial Disaggregation method, and the bias-corrected GCM outputs are then employed to drive the Soil and Water Assessment Tool hydrological model and project streamflow. After correction and downscaling, areal averages for future changes (relative to 1971-2000) of temperature and precipitation are found larger in CMIP6 than in CMIP5. The emblematic annual mean temperature of CMIP6 increases by 1.64-2.20 and 2.31-5.29 degrees C for the future period of 2026-2055 and 2066-2095, while the counterpart of CMIP5 is 1.92-2.39 and 1.68-4.76 degrees C, respectively. In terms of precipitation, for CMIP6, it increases by 3.45-4.70 and 6.77-15.40%, and for CMIP5 by 2.58-2.96 and 3.83-9.95%. It is further concluded that: (1) future streamflow will probably decrease less under CMIP6 than that under CMIP5 in most cases, and climate changes of this kind will affect regional water supply and security in the YRB; (2) uncertainty in the projected streamflow is dominated by GCMs uncertainty with the contribution rate of >75%; (3) the streamflow is more sensitive to precipitation changes in comparison with temperature changes in the near future. In contrast, streamflow reduction is more attributed to an increase in temperature with a contribution rate of almost >60% than in precipitation in the far future.

Automated summary

This study evaluates the performance of CMIP6 and CMIP5 models in simulating the hydrological regime in the Yellow River Basin (YRB). The results show that CMIP6 models predict larger changes in temperature and precipitation compared to CMIP5 models. It is concluded that future streamflow will likely decrease less under CMIP6 than CMIP5, and streamflow is more sensitive to precipitation changes in the near future.