Atmospheric carbon dioxide (CO₂) would be increasing much more if it were not for terrestrial carbon (C) uptake, fueling the drawdown of atmospheric CO₂ in vegetation and soil on decadal to centennial time scales. Here, we used a global Earth system model (BNU‐ESM) with two different CO₂ data sets (i.e., uniform CO₂ vs. non‐uniform CO₂ data sets) to simulate the responses of the C balance, particularly to the non‐uniform CO₂ effect. Under future conditions of 2071–2100, accounting for spatial variations of CO₂ concentrations resulted in 0.51 Pg C yr⁻¹ or 19% additional global net ecosystem production (NEP) inductions relative to the uniform conditions. The reduction in NEP in the future was mostly caused by the reduction in the Northern Hemisphere, within which summer was the season that accounted for the largest fraction of this reduction. Changes in NEP under future conditions differed largely to those under present conditions, resulting from changes in the circulation caused by the non‐uniform CO₂—for example, reductions in evapotranspiration limit water vapor contributions to the lower atmosphere, and substantially diminish convective precipitation, which led to decreased precipitation. Our findings call for more attention to be paid to the influence of spatial variations in CO₂ concentration—particularly in the Northern Hemisphere—to better constrain the projected C uptake under future conditions. Also, it highlights the fundamental importance of non‐uniform CO₂ in determining the pattern, response, and magnitude of C uptake through to 2100.

It is important to understand regional contributions to interannual and decadal variabilities of vegetation productivity. However, most studies of regional terrestrial carbon cycles focus on the contributions of regional ecosystems to the mean or trend of net primary production (NPP), rather than its interannual variability (IAV). In this study, the IAV of NPP is explored using the simulation of the Australian Community Atmospheric Biosphere Land Exchange model, version 2.1 (CABLE2.1), compared with an eight‐member Trends in Net Land–Atmosphere Carbon Exchanges (TRENDY) ensemble under present conditions (1951–2010). NPP IAV is also analyzed using only CABLE2.1 under future conditions (2041–2100). Under the present conditions, the Central China region (region CC) contributes the largest fraction (CABLE2.1, 28.2%; TRENDY, 33.3% ± 11.5%) of NPP IAV in China. Such an NPP IAV is strongly associated with circulation‐driven variations in precipitation in most of China (∼85%). During the future period, region CC still plays a key role in the national NPP IAV, at ∼24.6%. Although precipitation IAV is still the main driver regulating the NPP IAV for region CC under the future conditions, climate sensitivity of NPP IAV to precipitation IAV may weaken compared with those under the present conditions. Our results highlight the contribution of region CC to the NPP IAV of China as a whole.

Understanding how compound extremes affect terrestrial ecosystems is a major challenge in Earth system science. Although the combined effects of stressors are recognized, the manner in which the prestress state determines the basic response mechanism remains unclear. In this study, we used the “natural experiment” methodology to compare two major extreme events within a monsoon‐influenced, low‐latitude highlands setting to explain mechanistic changes in land‐atmosphere interactions. By analyzing an extensive set of remote sensing and reanalysis data with nonlinear structural equation modeling, we show that the ecosystem response shifted from a traditional water‐limited paradigm during the 2010 drought to an energy‐governed paradigm during the 2019 heatwave. Our results suggest that this transition is governed by the antecedent root zone soil moisture status, which acts as a tipping point fundamentally shifting the impact of atmospheric factors on canopy evapotranspiration screens, such as temperature and vapor pressure deficit. This study highlights a possible threshold‐type state dependence non‐linearity, which is lacking in major Earth System Models. Incorporating this “hydrological memory” is crucial for minimizing uncertainties in climate projections and for correctly assessing the vulnerability of ecosystems in a warming world.

To evaluate the ability of CMIP6 Earth System Models to simulate net biome production (NBP) changes caused by natural and man‐made forcing, the simulated NBP during the period 1901–2010 at global, hemispheric and regional scales was compared with the estimated NBP of the TRENDY ensemble. The annual NBP, globally and over the Northern Hemisphere and tropics, from the CMIP6 ensemble reflected well the TRENDY ensemble annual values from 1901 to 2010, and the correlation coefficient passed the 0.05 significance level. The annual NBP estimated by CMIP6 over the globe, Northern Hemisphere and tropics was 0.20 ± 0.46, 0.25 ± 0.34, and −0.02 ± 0.14 Pg C yr⁻¹, respectively; while from the TRENDY ensemble it was 1.04 ± 0.41, 0.55 ± 0.24, and 0.43 ± 0.20 Pg C yr⁻¹, respectively. The main weaknesses of the CMIP6 multi‐model ensemble simulation was the lower strength of NBP, especially at low latitudes. The simulated results showed higher soil respiration estimated by CMIP6 for these regions, especially in the Amazon Basin, than that by the TRENDY ensemble, which produced the greater NPB estimated by TRENDY. The CMIP6 ensemble exaggerated the increasing trend of carbon sinks between 30° and 60°N in the Northern Hemisphere after 1961, due to the stronger positive response of NPP (net primary production) in the high‐latitude Northern Hemisphere to global warming. The NBP during 1901–2010 could not be reproduced well by the CMIP6 ensemble in most sub‐regions, as evidenced by the failure to pass the statistical test at the 5% significance level in 70% of the sub‐regions in terms of the correlation coefficients with the TRENDY ensemble. In eastern Asia, for example, NBP was poorly estimated by the CMIP6 ensemble, as evidenced by negative correlation coefficients with the TRENDY ensemble.

The offshore region of East Asia has a crucial role in recycling precipitation, especially in the current context of a warming climate. This is because the atmospheric feedback from the sea offshore East Asia directly impacts and modifies precipitation patterns by influencing the seasonal cycles of the surface energy and water budgets. We used a regional climate model incorporating sea–air coupling to investigate and better understand these climate feedback mechanisms in East Asia. We identified a reduction in precipitation caused by sea-air coupling over East Asia during the time period 1991 − 2014 under present day conditions. Specifically, we observed an average decrease in precipitation of about 0.1 ± 0.40 mm day⁻¹ during June–July–August. This decrease in precipitation can be attributed to a combination of factors, including the effects of upward solar radiation, the asymmetry of the thermal contrast between the land and the sea, decreased evaporation in the southeastern ocean and the weakened transport of water vapor from the sea to the land. Our research suggests that the decrease triggered by sea–air coupling will be partially alleviated under future conditions, although not completely reversed, in terms of its impact on precipitation in eastern China. Although some relief is anticipated, the overall influence of sea–air coupling on patterns of precipitation in East Asia will persist, especially south of the Yellow River in eastern China.