Global assessment of agreement among streamflow projections using CMIP5 model outputs

Runoff outputs from 11 atmosphere-ocean general circulation models (AOGCMs) participating in the fifth phase of Coupled Model Intercomparison Project were used to evaluate the changes in streamflow and agreement among AOGCMs at the end of 21st century. Under the highest emission scenario (Representative Concentration Pathways (RCP) 8.5), high flow is projected to increase in northern high latitudes of Eurasia and North America, Asia, and eastern Africa, while mean and low flows are both projected to decrease in Europe, Middle East, southwestern United States, and Central America. Projected changes under RCP4.5 show similar spatial distribution but with lower magnitude. The model spread of projected changes, however, is found to be large under both scenarios. Bootstrapped Mann-Whitney-Wilcoxon U test revealed that projected changes of streamflow regimes are statistically not significant in 8-32% (19-59%) of the world under RCP8.5 (RCP4.5). The model agreement on projected increase or decrease in mean and high flows is stronger under RCP8.5 than that under RCP4.5. On the other hand, the projected changes in low flow are robust in both scenarios with strong model agreement. In similar to 7% (4%) of the world, high flow is projected to increase and low flow is projected to decrease, whereas in similar to 29% (13%) all mean, high, and low flows are projected to increase under RCP8.5 (RCP4.5).