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Anthropogenic impacts on widespread global soil moisture (SM) drying in the root zone layer during 1948-2005 were evaluated based on the Global Land Data Assimilation System version 2 (GLDAS-2) and global climate models from the Coupled Model Intercomparison Project Phase 5 using trend analysis and optimal fingerprint methods. Both methods show agreement that natural forcing alone cannot drive significant SM drying. There is a high probability (90%) that the anthropogenic climate change signal is detectable in global SM drying. Specifically, anthropogenic greenhouse gas forcing can lead to global SM drying by 2.1x10(-3)m(3)/m(3), which is comparable to the drying trend seen in Global Land Data Assimilation System version 2 (2.4x10(-3)m(3)/m(3)) over the past 58 years. Global SM drying is expected to continue in the future, given continuous greenhouse gas emissions.

Plain Language Summary Satellite observations and model simulations indicated widespread soil moisture (SM) drying in the root zone layer. Global-scale SM drying has also been corroborated by meteorological drought indices. SM drying can accentuate the intensity of heat waves under global warming. Recent record-breaking heat waves were amplified by SM drying, such as the 2003 European heat waves and 2010 Russia heat waves. The contributions of human activities to global-scale SM changes have not been comprehensively evaluated. There is a high probability (90%) that the anthropogenic climate change signal in global SM drying is detectable. Specifically, anthropogenic greenhouse gas forcing can lead to global SM drying by 2.1x10-3m3/m3, which is comparable to the drying trend seen in Global Land Data Assimilation System version 2 (2.4x10-3m3/m3) over the past 58years. Global SM drying is expected to continue in the future, given continuous greenhouse gas emissions.