Exploring the Future Cropland Exposure to Compound Drought and Heat Events from High-Resolution CCAM-ACS Simulations over Australia

Compound Drought and Heat Events (CDHEs) pose a growing threat to agricultural systems under a warming climate. This study evaluates mid-century shifts in CDHE characteristics and cropland exposure across Australia using high-resolution CCAM-ACS simulations for Shared Socioeconomic Pathway 1–2.6 (SSP1-2.6) and Shared Socioeconomic Pathway 3–7.0 (SSP3-7.0). An ensemble of seven bias-corrected regional climate models was used to compute the Standardized Precipitation Index (SPI) and Standardized Temperature Index (STI), from which CDHE characteristics were derived. Analyses were performed for the historical (1985–2014) and future (2030–2059) periods, and cropland exposure was quantified through the integration of gridded cropland fractions with CDHE occurrence across the eight Natural Resource Management (NRM) clusters. The findings reveal a nationwide intensification of compound drought–heat stress. CDHE frequency increases by approximately 15–30% under SSP1-2.6, with a sharper 20–60% escalation under SSP3-7.0. The strongest rises occur across the Murray-Basin, Central-Slopes, and East-Coast clusters. Event intensity strengthens by 10–25% in the low-emission future and by 30–50% in the high-emission scenario. Event duration also lengthens across most of Australia, indicating a 5–15% increase, while northern and eastern hotspots experience up to 20–25% longer events. The estimates show systematic rightward shifts across all CDHE metrics, reflecting higher probabilities of more frequent and energetically stronger events. When combined with projected cropland patterns, exposure increases markedly. Historical exposure (≈100–300 km² yr⁻¹) rises to 200–350 km² yr⁻¹ under SSP1-2.6 and up to 250–500 km² yr⁻¹ under SSP3-7.0, with the largest increases across southeastern and southwestern cropping belts. Several NRM clusters begin transitioning toward persistently high-exposure states by mid-century. The attribution analysis shows that most of the mid-century increase in cropland exposure is driven primarily by the climate-change component—far exceeding the contribution of cropland shifts—under both SSP1-2.6 and SSP3-7.0. Overall, the findings highlight a substantial escalation in compound drought–heat risk for Australian agriculture and underline the need for climate-resilient cropping systems and regional adaptation strategies.