Assessing Regional-Scale Heterogeneity in Blue-Green Water Availability under the 1.5 ° C Global Warming Scenario

The 2015 Paris Agreement outlined limiting global warming to 1.5 degrees C relative to the preindustrial levels, necessitating the development of regional climate adaptation strategies. This requires a comprehensive understanding of how the 1.5 degrees C rise in global temperature would translate across different regions. However, its implications on critical agricultural components, particularly blue and green water, remains understudied. This study investigates these changes using a rice -growing semiarid region in central India. The aim of this study is to initiate a discussion on the regional response of blue - green water at speci fi c warming levels. Using different global climate models (GCMs) and shared socioeconomic pathways (SSPs), the study estimated the time frame for reaching the 1.5 degrees C warming level and subsequently investigated changes in regional precipitation, temperature, surface runoff, and blue - green water. The results reveal projected reductions in precipitation and surface runoff by approximately 5% - 15% and 10% - 35%, respectively, along with decrease in green and blue water by approximately 12% - 1% and 40% - 10%, respectively, across different GCMs and SSPs. These fi ndings highlight 1) the susceptibility of blue - green water to the 1.5 degrees C global warming level, 2) the narrow time frame available for the region to develop the adaptive strategies, 3) the in fl uence of warm semiarid climate on the blue - green water dynamics, and 4) the uncertainty associated with regional assessment of a speci fi c warming level. This study provides new insights for shaping food security strategies over highly vulnerable semiarid regions and is expected to serve as a reference for other regional blue/green water assessment studies.