A mutivariate Framework for Assessing Compound Agroclimatic Extremes

Although European agriculture faces escalating threats from climate extremes, current risk assessments focus on single hazards, overlooking compounding effects that drive devastating agricultural losses. This study presents a novel framework for assessing compound agroclimatic extremes in potato production across Europe, utilizing crop-specific physiological thresholds rather than generic meteorological definitions. We employed copula methods for extreme precipitation-temperature events and vine copula approaches for dry-cold-heat and wet-cold-heat compound events to characterize 32 compound extreme combinations across duration, intensity, magnitude, and frequency dimensions using ERA5 reanalysis data (1990-2024). Our analysis reveals striking spatial heterogeneity with pronounced north-south gradients. Mediterranean regions experience persistent hot-dry events lasting 3-4 days on average, but Northern Europe faces brief but intense cold-dry and hot-dry extremes. Key findings reveal nonlinear risk amplification under triple compound events, which exhibit intensity values 4-13 times higher than double events and magnitude anomalies 2-4 times greater. This amplification stems from synergistic interactions among temperature, precipitation, and land-atmosphere processes that generate cascading feedback exceeding individual hazard impacts. Cold-dry extremes emerge as the dominant threat, occurring 5-10 times more frequently than cold-wet combinations and at least 10 times more frequently than hot-wet extremes across central and northern Europe. Joint return period analysis reveals that severe hot-dry events occur every 1-3 years in Mediterranean hotspots, while moderate cold-dry events occur every 1-5 years across most of Europe. These results fundamentally challenge single-hazard agricultural risk frameworks and underscore the urgent need for adaptation strategies accounting for compound events. Our methodology, integrating crop-specific thresholds with comprehensive temporal characterization, provides a scalable and transferable approach for assessing agricultural climate risk across diverse cropping systems. The findings offer actionable insights for European potato cultivation planning and climate adaptation policies, highlighting critical hotspot regions where compound extremes pose the greatest threat to agricultural productivity and food security.