Warming accelerates drought-flood oscillations and stratifies socioeconomic exposure

Anthropogenic warming intensifies the hydrological cycle, increasing the likelihood of drought and flood events. However, disaster assessments predominantly evaluate these hazards in isolation, obscuring the distinct physical characteristics and societal impacts of drought-flood alternations. Here, we integrate bias-corrected climate projections with hydrological and socioeconomic mapping to quantify the evolving dynamics of three drought-flood switching event types-drought-flood alternation events, drought-to-flood transitions, and flood-to-drought transitions-and their unequal burdens across warming levels from 1.5 to 4.5 °C in China, a region facing the world's most severe flood impacts. We show that warming systematically compresses transition intervals between drought and flood conditions, driving marked increases in the frequency and spatial extent of these event types. This physical acceleration amplifies socioeconomic exposure, revealing a stark distributional asymmetry. While wealthy regions experience the highest absolute exposure, lower-income populations face disproportionately high relative increases in human and economic exposure risks. Our results demonstrate that the temporal compression of hydrological extreme reversals creates a class of compound risk that reduces preparedness windows and stratifies vulnerability along socioeconomic lines. These findings underscore the urgency of incorporating rapid hydrological transitions into adaptation strategies to address the inequal escalation of climate risk, a critical dimension of vulnerability that has long been overlooked.