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Drought and atmospheric aridity pose large risks to ecosystem services and agricultural production. However, these factors are seldom assessed together as compound events, although they often occur simultaneously. Drought stress on terrestrial carbon uptake is characterized by soil moisture (SM) deficit and high vapor pressure deficit (VPD). We used in situ observations and 15 Earth system models to show that compound events with very high VPD and low SM occur more frequently than expected if these events were independent. These compound events are projected to become more frequent and more extreme and exert increasingly negative effects on continental productivity. Models project intensified negative effects of high VPD and low SM on vegetation productivity, with the intensification of SM exceeding those of VPD in the Northern Hemisphere. These results highlight the importance of compound extreme events and their threats for the capability of continents to act as a carbon sink. Drought, atmospheric aridity, and heat waves have been, and will continue to be, large threats to humans and natural systems (1, 2). Decreased soil moisture (SM) and increased atmospheric aridity have been recognized as two main drought-related limits of terrestrial water use and carbon uptake (3). Atmospheric aridity is typically assessed using the vapor pressure deficit (VPD), determined by the combination of atmospheric humidity and temperature. In response to high VPD, plants tend to reduce their stomatal conductance to minimize water loss (4). Decreased SM also triggers plant stomata to partially close to prevent hydraulic conductivity loss (5). Recent observational and modeling studies have emphasized that vegetation carbon uptake may be more sensitive to high VPD than to low SM (3, 6). While the effects of VPD and SM on vegetation are often evaluated as if they were independent, high VPD and low SM events are well known to often occur simultaneously (7–9). The tendency for high VPD and low SM events to co-occur may cause drought- and heat-driven reductions in vegetation productivity to be much greater than if VPD and SM did not covary. It is crucial to evaluate the coupling of VPD and SM, especially the co-occurrence of extreme high VPD and low SM events globally, and the impact on terrestrial carbon uptake. Specifically, the intensity, frequency, and risks of compound drought and atmospheric aridity events, which have not been assessed before, are of great importance for terrestrial ecosystems, especially under future climate change. Compound drought and aridity events are driven by a series of complementary physical processes. Low SM reduces evapotranspiration, leading to higher temperature (10, 11) and VPD as a result of reduced evaporative cooling and near-surface humidity. Heightened VPD, in turn, positively forces land evapotranspiration, further accelerating the depletion of SM, compared to low VPD conditions. Co-occurring regional drought and heat wave extremes have greatly increased in frequency and intensity since the mid-1900s, despite the fact that there may not be a notable negative trend in the global mean SM (12, 13). The frequency of compound extremes is expected to continue to increase as a result of the projected warming trends (14), potentially exacerbating the impacts of drought on terrestrial ecosystems. Here, we show that (i) compound VPD and SM extremes occur much more frequently than expected if VPD and SM were not intimately coupled, (ii) this coevolution of drought and aridity results in substantial ecosystem carbon losses, and (iii) the impacts of these compound extremes will strengthen in the future. We used in situ observations from 66 flux tower sites spanning various climates and plant functional types and simulations from 15 Earth system models (ESMs), which were developed as part of the Coupled Model Intercomparison Project Phase 5 (CMIP5) (see the Supplementary Materials) to evaluate the co-occurrence probability of extreme high VPD and low SM and the impact of this covariation on terrestrial carbon uptake during the warm season. To assess effects on the terrestrial carbon budget, we used net ecosystem productivity (NEP) and its components: photosynthesis [gross primary productivity (GPP)] and respiration [total ecosystem respiration (TER)]. Drought stress is often measured according to precipitation deficits, and previous compound events have focused on drought and high temperature (12, 15, 16). In this study, we used extreme low SM and high VPD to represent drought and atmospheric aridity, respectively. We evaluated the compound effects of co-occurring low SM and high VPD on terrestrial carbon uptake as these variables directly affect plant stomatal conductance and photosynthetic carbon assimilation (3).