Emergence of significant soil moisture depletion in the near future

Abstract

Declining soil moisture related to climate change can greatly affect social, economic, environmental, and hydrological processes, as well as extreme weather events. Hence, it is imperative to understand the timing of significant soil moisture drying under future climate change. Compared to spatial variations in soil moisture drying, however, our understanding of temporal variations remain unclear. In the present study, the timing of significant soil moisture depletion (SSD) is predicted using the soil moisture projection (0-50 cm depth) from the 30 Inter-Sectoral Impact Model Intercomparison Project fast-track outputs under the representative concentration pathways (RCPs) 2.6 and 8.5. Under both RCP scenarios, the ensemble medians of the projections show the emergence of the timing of SSD in Western Europe, Eastern United States, South America, Sub-Saharan Africa, Australia, and Southern China over 40 years (<year 2060). In 2020, the Eastern United States, Australia, and Southern China already experienced SSD. These findings concur with those of previous observational studies on rapid droughts in the mid to late 2010s. On average, approximately 15% and 29% of the global land area will experience SSD under RCP 2.6 and RCP 8.5, respectively, by the end of the 21st century. A comparison of the timing of SSD in under RCP 8.5 with the timing of the global warming target (1.5 degrees C) shows that approximately 10% of the global land area will experience SSD before the 1.5 degrees C warming target is achieved. However, this will double to approximately 23% if the global warming level reaches 2 degrees C. The results of this study suggest that near-future predictions of the timing of SSD should be considered to mitigate its negative impacts.