Climate Change and Drought: the Soil Moisture Perspective

We review the extensive and sometimes conflicting recent literature on drought changes under global warming. We focus on soil moisture deficits, which are indicative of associated impacts on ecosystems. Soil moisture is a key state variable of the land surface, reflecting complex interactions between the water, energy, and carbon cycles. Offline projections relying on soil moisture proxy metrics indicate dramatic future drought increases, often interpreted as primarily driven by warming-induced increases in evaporative demand. However, such results appear inconsistent with other trends in the land–atmosphere system, including soil moisture, vegetation, and evapotranspiration. Recent studies begin to explain these discrepancies, highlighting the importance of soil–vegetation–atmosphere coupling, unaccounted for in offline projections. Future changes in soil moisture droughts should preferably be assessed with prognostic model outputs rather than offline heuristics and be interpreted in the context of the coupled soil–vegetation–atmosphere system.