Global perspective of changes in the terrestrial hydrologic cycle using different data products

Changes in the terrestrial hydrologic cycle determine the future availability of water around the world, affecting various aspects of society. Accurate estimation of these changes is essential for effective implementation of water management policies. A major source of uncertainty in such estimates is the data products used for analysis. This study provides a global perspective of changes in water availability in terms of Precipitation minus Evapotranspiration (P-E) using three data sources, namely reanalysis (ERA5-Land), hydrological modelling (TerraClimate), and simulations of eight Global Climate Models (GCMs; CMCC-CM2, CNRM-CM6, EC-Earth3P, ECMWF-IFS, HadGEM3-GC31, IPSL-CM6A, MPI-ESM1, and MRI-AGCM3 ). The period of analysis (1960-2014) is divided into two epochs, and the magnitude of change is analyzed by the percent change in the mean and increasing/decreasing trend over the 55-year period. In general, all three data products successfully capture the climatological mean of P-E with comparatively higher values for the equatorial regions. However, when comparing the intensity of changes the results provided by the three data sources differ significantly, especially for regions at higher latitudes. Projections from various GCMs show significant rise in the precipitation for the higher latitudes, which will also affect the extent of P-E and increase the uncertainty over the changes in water availability. It is critical to find reliable data sources for the historical period to increase confidence in future projections and to successfully implement various bias correction techniques wherever necessary.