Future socio-ecosystem productivity threatened by compound drought–heatwave events

Compound drought–heatwave (CDHW) events are one of the worst climatic stressors for global sustainable development. However, the physical mechanisms behind CDHWs and their impacts on socio-ecosystem productivity remain poorly understood. Here, using simulations from a large climate–hydrology model ensemble of 111 members, we demonstrate that the frequency of extreme CDHWs is projected to increase by tenfold globally under the highest emissions scenario, along with a disproportionate negative impact on vegetation and socio-economic productivity by the late twenty-first century. By combining satellite observations, field measurements and reanalysis, we show that terrestrial water storage and temperature are negatively coupled, probably driven by similar atmospheric conditions (for example, water vapour deficit and energy demand). Limits on water availability are likely to play a more important role in constraining the terrestrial carbon sink than temperature extremes, and over 90% of the global population and gross domestic product could be exposed to increasing CDHW risks in the future, with more severe impacts in poorer and more rural areas. Our results provide crucial insights towards assessing and mitigating adverse effects of compound hazards on ecosystems and human well-being.