Emissions from land use and land cover change are a key component of the global carbon cycle. However, models are required to disentangle these emissions from the land carbon sink, as only the sum of both can be physically observed. Their assessment within the yearly community-wide effort known as the “Global Carbon Budget” remains a major difficulty, because it combines two lines of evidence that are inherently inconsistent: bookkeeping models and dynamic global vegetation models. Here, we propose a unifying approach that relies on a bookkeeping model, which embeds processes and parameters calibrated on dynamic global vegetation models, and the use of an empirical constraint. We estimate that the global CO₂ emissions from land use and land cover change were 1.36±0.42 PgC yr^−1 (1σ range) on average over the 2009–2018 period and reached a cumulative total of 206±57 PgC over the 1750–2018 period. We also estimate that land cover change induced a global loss of additional sink capacity – that is, a foregone carbon removal, not part of the emissions – of 0.68±0.57 PgC yr^−1 and 32±23 PgC over the same periods, respectively. Additionally, we provide a breakdown of our results' uncertainty, including aspects such as the land use and land cover change data sets used as input and the model's biogeochemical parameters. We find that the biogeochemical uncertainty dominates our global and regional estimates with the exception of tropical regions in which the input data dominates. Our analysis further identifies key sources of uncertainty and suggests ways to strengthen the robustness of future Global Carbon Budget estimates.

中文翻译：

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土地使用和土地覆被变化的历史CO ₂排放量及其不确定性

土地使用和土地覆被变化产生的排放是全球碳循环的关键组成部分。但是，需要模型才能将这些排放物从陆地碳汇中解散出来，因为只能从物理上观察到两者的总和。他们在称为“全球碳预算”的社区年度工作中进行评估。仍然是一个主要困难，因为它结合了本质上不一致的两类证据：簿记模型和动态全球植被模型。在这里，我们提出了一种基于簿记模型的统一方法，该模型嵌入了在动态全球植被模型上校准的过程和参数以及经验约束的使用。我们估计，来自土地利用和土地覆被变化的全球CO ₂排放量为1.36±0.42â???? PGCA ????年^{â???? 1}（1 Ï?? 范围）上平均在2009A ???? 2018段和累计达到206A±57 â???? PGC在1750年至2018年期间。我们还估计，土地覆被的变化会导致全球范围内额外的水槽容量的丧失– 就是说，已放弃的碳清除，不是排放的一部分？的0.68A±0.57 â???? PGCA ????年^{â???? 1}和32A±23●PgC分别在同一时期内。此外，我们提供了结果不确定性的细目分类，包括土地用途和土地覆被变化数据集（用作输入数据）和模型的生物地球化学参数等方面。我们发现，生物地球化学不确定性主导着我们的全球和区域估计值，但输入数据占主导的热带地区除外。我们的分析进一步确定了不确定性的主要来源，并提出了增强未来全球碳预算估计的稳健性的方法。