We suggest that the term “megadroughts” be reserved for “persistent, multi-year drought events that are exceptional in terms of severity, duration, or spatial extent when compared to other regional droughts during the instrumental period or the Common Era”.

Past megadroughts caused major ecological and societal disturbances over the last two millennia and were forced primarily by persistent ocean states, with possible secondary contributions from internal atmospheric variability, volcanic and solar forcing, and land–atmosphere interactions.

Some of the most active megadrought regions in the past are also areas where anthropogenic climate change is projected to increase future drought risk through declines in precipitation, increases in evaporative demand, and/or changes in plant water use.

Megadroughts have the potential to substantially strain modern water-management systems, although understanding of the risks of such events, and their ultimate impacts, is still limited by imperfect knowledge of past and future megadrought dynamics.