Increasing meteorological drought under climate change reduces terrestrial ecosystem productivity and carbon storage

The terrestrial biosphere absorbs about 30% of the CO2 emitted by human activities each year. The persistence of such a carbon sink, however, depends on vegetation responses to future changes in water availability. While evidence suggests an increasing frequency and intensity of meteorological droughts, the potential systematic impact on vegetation productivity and its associated carbon absorption is unquantified. Using data from CMIP6 models and multiple meteorological drought indices and comparing the historical baseline (1851–2000) to the end of the century (2076–2100), we show that the global mean drought-associated reductions in vegetation productivity are projected to increase by 2.3 times under a sustainable development scenario (shared socioeconomic pathway [SSP] 1–2.6) and 3.5 times under fossil-fueled development (SSP5–8.5). These drought-induced productivity losses are greater than the predicted increase in productivity from greater CO2 “fertilization,” particularly for cropland. Our results indicate that the exacerbation of meteorological droughts under future warming will risk global food security and may transform the terrestrial ecosystem from a carbon sink into a carbon source.