The temperature dependence of global photosynthesis and respiration determine land carbon sink strength. While the land sink currently mitigates ~30% of anthropogenic carbon emissions, it is unclear whether this ecosystem service will persist and, more specifically, what hard temperature limits, if any, regulate carbon uptake. Here, we use the largest continuous carbon flux monitoring network to construct the first observationally derived temperature response curves for global land carbon uptake. We show that the mean temperature of the warmest quarter (3-month period) passed the thermal maximum for photosynthesis during the past decade. At higher temperatures, respiration rates continue to rise in contrast to sharply declining rates of photosynthesis. Under business-as-usual emissions, this divergence elicits a near halving of the land sink strength by as early as 2040.

全球光合作用和呼吸作用的温度依赖性决定了陆地碳汇的强度。虽然目前土地汇减少了约 30% 的人为碳排放，但尚不清楚这种生态系统服务是否会持续存在，更具体地说，是什么硬温度限制（如果有的话）调节碳吸收。在这里，我们使用最大的连续碳通量监测网络来构建第一个观测得出的全球陆地碳吸收温度响应曲线。我们表明，在过去十年中，最热季度（3 个月期间）的平均温度超过了光合作用的热最大值。在较高温度下，呼吸速率继续上升，而光合作用速率急剧下降。在一切照旧的排放下，