The Effect of Global Warming on Water Availability

The trend in global near-surface air temperature tends to serve as the de facto measure of anthropogenic climate change impacts. However, changes in the global water cycle brought on by climate change are bound to be far more critical to socio-economic-environmental well-being. In advance of the forthcoming Coupled Model Intercomparison Project Phase 6 (CMIP6), this study takes a holistic look back on results from the CMIP5 simulations in regard to past and projected water budgets across the world’s largest river basins. Using all available models and realizations for: Atmospheric Model Intercomparison Project (AMIP), historical, Earth System Model (ESM)-historical, Representative Concentration Pathways (RCP) 8.5 and ESM-RCP 8.5 experiments, we quantify for each river basin the multi-model consensus water budget terms and characterize individual model performance. Individual and multi-model mean skills at annual and seasonal timescales are evaluated through comparison of AMIP results against best available estimates, including: MERRA-2, ERA-INT, JRA-55, and the Princeton Global Forcing VIC datasets. The effect of dynamic vegetation on water availability and variability will serve as one specific point of departure for in-depth analyses, based upon comparisons between ESM-enabled and ESM-disabled model simulations.