Amplified socioeconomic impacts of compound drought–heatwave events

Isolated and compound climate extremes, such as droughts and heatwaves, are intensifying under global warming. Although recent studies have advanced the physical understanding and classification of compound events, their socioeconomic impacts remain poorly quantified at the global scale using disaster record databases. Building on evidence that compound drought–flood events can generate impacts substantially larger than those from isolated hazards, this study extends the inquiry by providing a global assessment of the socioeconomic impacts of compound drought–heatwave (CDH) events.

To achieve this, we use the Emergency Events Database (EM-DAT) for the period 1960–2025 and analyse reported drought and heatwave disasters at the global scale. CDH events are identified using complementary approaches, including overlapping drought and heatwave records within the same location (top-level administrative unit) and the “Associated Types” information in EM-DAT, thereby allowing assessment of sensitivity to event definition. Furthermore, EM-DAT drought events are compared with heatwave conditions derived from the ERA5 reanalysis to evaluate consistency between reported impacts and climatic co-occurrence. Socioeconomic impacts are quantified using the affected population, human fatalities, and reported damages.

Preliminary results show a clear increase in the number of reported areas affected by CDH events globally, particularly since the mid-2010s. Moreover, CDH events are consistently associated with greater impacts than single hazards. Specifically, using matching events within EM-DAT, compound events exhibit greater total damage, while fatalities during heatwaves increase by up to a factor of five when drought conditions co-occur. Furthermore, when drought impacts from EM-DAT are associated with heatwaves identified in ERA5, the damage and affected population are, respectively, two to four times higher than for isolated drought events.

Taken together, these findings provide global-scale evidence that co-occurring droughts and heatwaves substantially amplify socioeconomic impacts. This underscores the need to explicitly account for compound extremes in climate risk assessment, adaptation planning, and disaster risk reduction.