The surface warming response to carbon emissions is diagnosed using a suite of Earth system models, 9 CMIP6 and 7 CMIP5, following an annual 1\% rise in atmospheric CO$_2$ over 140 years. This surface warming response defines a climate metric, the Transient Climate Response to cumulative carbon Emissions (TCRE), which is important in estimating how much carbon may be emitted to avoid dangerous climate. The processes controlling these intermodel differences in the TCRE are revealed by defining the TCRE in terms of a product of three dependences: the surface warming dependence on radiative forcing (including the effects of physical climate feedbacks and planetary heat uptake), the radiative forcing dependence on changes in atmospheric carbon and the airborne fraction. Intermodel differences in the TCRE are mainly controlled by the thermal response involving the surface warming dependence on radiative forcing, which arise through large differences in physical climate feedbacks that are only partly compensated by smaller differences in ocean heat uptake. The other contributions to the TCRE from the radiative forcing and carbon responses are of comparable importance to the contribution from the thermal response on timescales of 50 years and longer for our subset of CMIP5 models and 100 years and longer for our subset of CMIP6 models. Hence, providing tighter constraints on how much carbon may be emitted based on the TCRE requires providing tighter bounds for estimates of the physical climate feedbacks, particularly from clouds, as well as to a lesser extent for the other contributions from the rate of ocean heat uptake, and the terrestrial and ocean cycling of carbon.

中文翻译：

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通过物理反馈、热吸收和碳循环控制对排放的瞬态气候响应

在 140 年来大气 CO$_2$ 每年增加 1% 之后，使用一套地球系统模型 9 CMIP6 和 7 CMIP5 来诊断表面变暖对碳排放的响应。这种地表变暖响应定义了一个气候指标，即累积碳排放的瞬态气候响应 (TCRE)，这对于估计可能排放多少碳以避免危险气候很重要。控制 TCRE 中这些模型间差异的过程通过根据三个依赖项的乘积定义 TCRE 来揭示：地表变暖对辐射强迫的依赖（包括物理气候反馈和行星热量吸收的影响），辐射强迫对辐射强迫的依赖大气碳和空气传播部分的变化。TCRE 的模式间差异主要受热响应控制，该热响应涉及地表变暖对辐射强迫的依赖，这是由物理气候反馈的巨大差异引起的，而海洋热吸收的较小差异仅部分补偿了这些差异。辐射强迫和碳响应对 TCRE 的其他贡献与 CMIP5 模型子集 50 年和更长时间尺度上的热响应贡献以及 CMIP6 模型子集 100 年和更长时间尺度上的热响应贡献相当重要。因此，根据 TCRE 对可能排放的碳量提供更严格的限制，需要为物理气候反馈的估计提供更严格的界限，特别是来自云，