Changes in Compound Hot-Dry Extremes and Their Exposures under Climate Change

Abstract Compound hot-dry extremes (CHDEs) impose disproportionate impacts on water resources, agriculture, and human health exceeding that of individual extremes. Understanding their evolution under climate change is critical for adaptation, yet several existing assessments relies largely on statistically downscaled products with substantial uncertainties. We present the first comprehensive global assessment of CHDEs using four bias-corrected experiments from the High Resolution Model Intercomparison Project (HighResMIP) at 0.5° resolution. Analysing historical (1980–2014) and future (2015–2050) patterns across low (1.0σ), moderate (1.5σ), and high (2.0σ) intensities for hot extremes and six-month droughts. Globally, CHDE coverage exceeded their baseline thresholds between 2010–2014 across all intensities, confirming intensification is already underway. By mid-century, global coverage of low intensity extremes is projected to increase by ~ 50%, moderate intensities to triple, and high intensities to increase five-fold under the highres-future scenario. The agricultural sector is also exposed during critical crop development periods, with some major breadbasket regions experiencing 2-4-fold increases in CHDEs. Tropical and subtropical regions emerged as global hotspots, while some northern latitudes are also projected to see a slight reduction despite the ongoing overall warming trends. These findings underscore urgency for enhanced preparedness, as CHDEs have transitioned from projected risks to observable present-day phenomena.