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Atmospheric drought indices in future projections

Abstract:

In this Perspective we critically discuss future drought projections, focusing on key issues related to the concept of drought and its frequent confusion with aridity. We address the common misunderstanding between drought metrics and drought indices, as well as misconceptions about what drought indices represent. Our analysis emphasizes the role of atmospheric evaporative demand in shaping future drought severity, along with its drivers, impact processes, and responses to global warming, while highlighting related observational and theoretical challenges. We also shed light on the uncertainties and limitations of Earth system models (ESMs) in assessing future drought severity. We explore the complexities of ESMs in accurately representing plant physiological and hydrological processes, which are crucial for evaluating drought severity. Our discussion also delves into the nuanced effects of atmospheric CO<inf>2</inf> concentrations on these processes and on water dynamics within ESMs, helping to clarify conceptual issues related to atmospheric drought indices. Finally, we advocate for a balanced evaluation of drought metrics, emphasizing the importance of considering multiple atmospheric processes in drought projections.