Changes in terrestrial water stress and contributions of major factors under temperature rise constraint scenarios

The Paris agreement adopted at the 21st Conference of Parties of the United Nations Framework Convention on Climate Change stipulates 2 and 1.5 °C targets, but their consistency with sustainable development is poorly understood. This study focuses on water stress defined by annual water consumption-to-availability ratio (CAR) and analyzes the CAR changes for 32 global regions during this century for scenarios of the 2 and 1.5 °C targets. It also estimates contributions of major factors behind such change for addressing the adaptation planning. The results show that the CARs in many (i.e., 25) regions remain very small (less than 0.1) regardless of the future temperature level. For the other seven regions, the CARs undergo significant changes, while the changes and contributing factors to them are different by region and the future temperature level. Possible adaptation strategies are given for regions of significantly increasing CARs. For instance, in Afghanistan and Pakistan and South Africa, the CARs increase mainly due to increases in irrigation water associated with socioeconomic development (i.e., food demand growth). Decreases in water availability and increases in irrigation water due to climate change also contribute to the CAR increases after 2030. The contributions of other factors (i.e., demand changes in municipal water, water for electricity generation, other industrial water, and water for livestock) are small. In these regions, securing water resources as well as irrigation water conservation are important to avoid worsening of the CAR. Adaptation strategy recommendations for other regions are also presented.