Gross primary production (GPP) has been identified as the largest terrestrial carbon flux and the major driver of the growing biosphere uptake of carbon. Factorial simulations using several biosphere models have been used to estimate the effects of long‐term (>50 years) climate change on global terrestrial GPP. However, no study has integrated large‐ensemble climate simulation data into a biosphere model to realistically estimate global terrestrial GPP with associated uncertainty. Here we present a novel approach to estimate the global terrestrial long‐term GPP with associated climate data‐induced uncertainty that combines a diagnostic‐type biosphere model with a large‐ensemble climate simulation data set. We distinguish the effects of recent anthropogenic activity on global GPP (the anthropogenic GPP effect) from the effects of interannual climate variability (the natural GPP effect) by comparing GPP model estimates forced by historical and “nonwarming” climate data. We provide evidence for an increasing anthropogenic effect on global terrestrial GPP. The anthropogenic GPP effect is driven by CO₂ fertilization, which is projected to weaken or saturate by 2050–2150, depending on the representative concentration pathway scenario used. Model results suggest that shortwave radiation couples with El Niño–Southern Oscillation conditions and volcanic eruptions to drive the natural GPP effect. Because shortwave radiation at the surface is related to cloud cover, we encourage future studies to focus on cloud‐radiation feedbacks on the carbon cycle.

中文翻译：

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人为活动对全球陆地总初级生产力的影响

初级生产总值（GPP）已被确定为最大的陆地碳通量，也是生物圈吸收碳的主要动力。使用几种生物圈模型进行的析因模拟已用于估算长期（> 50年）气候变化对全球陆地GPP的影响。但是，尚无研究将大集合气候模拟数据整合到生物圈模型中，以实际估算具有相关不确定性的全球陆地GPP。在这里，我们提出了一种新颖的方法来估计全球陆地长期GPP及其相关的气候数据导致的不确定性，该方法结合了诊断型生物圈模型和大型整体气候模拟数据集。通过比较由历史和“非变暖”气候数据强迫产生的GPP模型估计，我们将年度人为活动对全球GPP的影响（人为GPP效应）与年际气候变化的影响（自然GPP效应）区分开。我们提供了对全球陆地GPP不断增加的人为影响的证据。人为GPP效应是由CO驱动的₂施肥，预计将在2050年至2150年间减弱或饱和，这取决于所使用的代表性浓度途径情景。模型结果表明，短波辐射与厄尔尼诺-南方涛动条件和火山喷发相结合，从而推动了自然GPP效应。由于地表的短波辐射与云层覆盖有关，因此我们鼓励未来的研究集中在碳循环的云层辐射反馈上。