Cascading impacts of compound drought-heat extremes on global gross primary production

Anthropogenic warming climate-induced heat, drought, and compound heat-drought extremes and their damaging impacts on global vegetation productivity have sparked widespread concerns, while the spatially-variable responses of Gross Primary Production (GPP) to these extremes under warming levels still remain uncertain. Using grid GPP data, Coupled Model Intercomparison Project Phase 6 (CMIP6) outputs and Copula functions, we evaluate probability responses of extreme negative anomalies of GPP (ENAG) for regionally-varying vegetation types to different intensities of drought, heat and compound drought-heat events against different warming levels, i.e. 2, 3, 4 °C. We find cascading impacts of drought superimposed heat on global ENAG probability, but regionally-varying effects of heat superimposed drought. Meanwhile, we find augmented effects of compound drought-heat events on vegetation in low-latitude regions as compared to drought alone. Given heightened warming levels from 2 °C to 4 °C, the probability of globally-averaged ENAG can be anticipated to increase by 0.54%, 0.82%, and 1.12% under drought, heat, and compound drought-heat conditions, respectively. Specifically, enduring warming climate can inflict greater negative impacts on evergreen broadleaf forests, savannas and grasslands. We also identify typical vulnerable regions to drought, heat and compound drought-heat events under different warming levels such as central North America, central Africa, central Europe, Northwest Asia, East Asia, Southeast Asia, and southwestern and southeastern Australia. These findings highlight regionally variable impacts of drought, heat and compound drought-heat events on GPP under different warming levels. Graphical Abstract