To determine the remaining carbon budget, a new framework was introduced in the Intergovernmental Panel on Climate Change's Special Report on Global Warming of 1.5° C (SR1.5). We refer to this as a `segmented' framework because it considers the various components of the carbon budget derivation independently from one another. Whilst implementing this segmented framework, in SR1.5 the assumption was that there is a strictly linear relationship between cumulative CO2 emissions and CO2-induced warming i.e. the TCRE is constant and can be applied to a range of emissions scenarios. Here we test whether such an approach is able to replicate results from model simulations that take the climate system's internal feedbacks and non-linearities into account. Within our modelling framework, following the SR1.5's choices leads to smaller carbon budgets than using simulations with interacting climate components. For 1.5° C and 2° C warming targets, the differences are 50 GtCO2 (or 10%) and 260 GtCO2 (or 17%), respectively. However, by relaxing the assumption of strict linearity, we find that this difference can be reduced to around 0 GtCO2 for 1.5° C of warming and 80 GtCO2 (or 5%) for 2.0° C of warming (for middle of the range estimates of the carbon cycle and warming response to anthropogenic emissions). We propose an updated implementation of the segmented framework that allows for the consideration of non-linearities between cumulative CO2 emissions and CO2-induced warming.

中文翻译：

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累积 CO ₂排放量和 CO ₂引起的变暖之间的非线性对评估剩余碳收支的影响

为了确定剩余的碳预算，政府间气候变化专门委员会关于全球变暖 1.5°C 的特别报告 (SR1.5) 引入了一个新框架。我们将其称为“分段”框架，因为它独立地考虑了碳预算推导的各个组成部分。在实施此分段框架时，SR1.5 中的假设是累积 CO2 排放与 CO2 引起的变暖之间存在严格的线性关系，即 TCRE 是恒定的，可以应用于一系列排放情景。在这里，我们测试这种方法是否能够复制将气候系统的内部反馈和非线性考虑在内的模型模拟结果。在我们的建模框架内，遵循 SR1.5' 与使用具有相互作用气候成分的模拟相比，s 的选择导致更少的碳预算。对于 1.5°C 和 2°C 升温目标，差异分别为 50 GtCO2（或 10%）和 260 GtCO2（或 17%）。然而，通过放宽严格线性的假设，我们发现，升温 1.5°C 时这种差异可以减小到 0 GtCO2 左右，升温 2.0°C 时可以减小到 80 GtCO2（或 5%）（对于碳循环和变暖对人为排放的反应）。我们提出了分段框架的更新实施方案，允许考虑累积 CO2 排放和 CO2 引起的变暖之间的非线性。然而，通过放宽严格线性的假设，我们发现，升温 1.5°C 时这种差异可以减小到 0 GtCO2 左右，升温 2.0°C 时可以减小到 80 GtCO2（或 5%）（对于碳循环和变暖对人为排放的反应）。我们提出了分段框架的更新实施方案，该框架允许考虑累积 CO2 排放和 CO2 引起的变暖之间的非线性。然而，通过放宽严格线性的假设，我们发现，升温 1.5°C 时这种差异可以减小到 0 GtCO2 左右，升温 2.0°C 时可以减小到 80 GtCO2（或 5%）（对于碳循环和变暖对人为排放的反应）。我们提出了分段框架的更新实施方案，该框架允许考虑累积 CO2 排放和 CO2 引起的变暖之间的非线性。