Residual emissions are an important category of analysis in climate targets and scenarios, describing the emissions that would need to be compensated by carbon dioxide removal to reach net zero CO₂. This article sheds light on the size and composition of residual emissions in integrated assessment modelling (IAM) scenarios at net-zero CO₂, using the Intergovernmental Panel on Climate Change 6th assessment report (AR6) scenario database. I find that IAMs depict residual greenhouse gas emissions levels of 16 [12–26] GtCO₂e/yr across below 1.5 °C, below 1.5 °C with overshoot, and below 2 °C scenarios—representing gross emissions reductions of 72 [55–78] % from 2020 to the point of net zero CO₂. Emissions from livestock, agriculture, transport, waste and industrial processes remain most prevalent at net zero, with scenario averages tending to depict significantly lower reduction rates and higher residual emissions than those recently published in corporate net zero standards. Nonetheless, scenarios depict a wide range of outcomes across all of these ‘hard-to-abate’ sectors, with lower values characterised by demand-side shifts in the food and energy system, alongside the rapid electrification of end-use sectors and limits on CDR scaling. Current scenario reporting does not easily facilitate the calculation of gross emissions from the AR6 database, which would be a prerequisite to a more systematic exploration of the residual emissions frontier and its implications for climate policy.

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净零二氧化碳综合评估情景中残余排放的规模和构成

残余排放是气候目标和情景中的一个重要分析类别，描述了需要通过二氧化碳去除来补偿以达到净零CO ₂的排放。本文利用政府间气候变化专门委员会第六次评估报告 (AR6) 情景数据库，揭示了净零 CO ₂综合评估模型 (IAM) 情景中残余排放的规模和构成。我发现 IAM 描述的残余温室气体排放水平为 16 [12–26] GtCO ₂ e/yr，涵盖低于 1.5 °C、低于 1.5 °C 的超调和低于 2 °C 的情景，代表总排放量减少 72 [55 –78]%，从 2020 年到净零 CO ₂点。畜牧业、农业、运输、废物和工业过程的排放仍然最普遍处于净零排放，情景平均值往往显示比最近公布的企业净零标准显着较低的减排率和较高的残余排放量。尽管如此，情景描绘了所有这些“难以减少”行业的广泛结果，其中较低的价值以食品和能源系统的需求方转变为特征，同时终端使用行业的快速电气化和对电力的限制CDR 缩放。当前的情景报告不容易促进 AR6 数据库中总排放量的计算，而这将是更系统地探索残余排放边界及其对气候政策影响的先决条件。