Causal Impacts of El Niño–Southern Oscillation on Global Soil Moisture Over the Period 2015–2100

Abstract Soil moisture is an important element of the Earth system that influences both mean and extreme climate, hydrological cycle, vegetation growth and agricultural production. Therefore, it is essential to understand the factors that drive soil moisture variability. Soil moisture variations have been shown to be affected by the El Niño–Southern Oscillation (ENSO) in several regions. However, the causal impacts of ENSO on global soil moisture remain elusive, particularly regarding the future periods under warming environment. Here we assessed the causal effects of ENSO on soil moisture at the global scale over the 2015–2100 period using data from Coupled Modeling Intercomparison Project Phase 6 (CMIP6) models. We find that ENSO is likely to have causal impacts on soil moisture over areas of northern Australia, parts of eastern and southern Africa, Southeast Asia, large parts of South America, middle and western Asia, and parts of southern North America. The results show low consistency between CMIP6 models for the causal impacts of ENSO over Southeast Asia while the models' consensus is higher over eastern Africa, western Asia, Australia, south central North America, and South America. In addition, our results suggested an expansion in the spatial influences of ENSO on regional soil moisture for the future period 2015–2100 compared to the historical period 1915–2000. As soil moisture is an essential part of the water cycle and prediction of ENSO events is achievable, these results might have implications for regional water resources management in the future.