Estimating the cost to society from a ton of CO 2 —termed the social cost of carbon (SCC)—requires connecting a model of the climate system with a representation of the economic and social effects of changes in climate, and the aggregation of diverse, uncertain impacts across both time and space. A growing literature has examined the effect of fundamental structural elements of the models supporting SCC calculations. This work has accumulated in a piecemeal fashion, leaving their relative importance unclear. Here, we perform a comprehensive synthesis of the evidence on the SCC, combining 1,823 estimates of the SCC from 147 studies with a survey of authors of these studies. The distribution of published 2020 SCC values is wide and substantially right-skewed, showing evidence of a heavy right tail (truncated mean of $132). ANOVA reveals important roles for the inclusion of persistent damages, the representation of the Earth system, and distributional weighting. However, our survey reveals that experts believe the literature underestimates the SCC due to an undersampling of model structures, incomplete characterization of damages, and high discount rates. To address this imbalance, we train a random forest model on variation in the literature and use it to generate a synthetic SCC distribution that more closely matches expert assessments of appropriate model structure and discounting. This synthetic distribution has a mean of $283 per ton CO 2 for a 2020 pulse year (5% to 95% range: $32 to $874), higher than most official government estimates, including a 2023 update from the U.S. EPA.

中文翻译：

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由于结构模型的变化和不确定性，证据的综合产生了高碳的社会成本


估计一吨 CO 2 给社会带来的成本——称为碳的社会成本 （SCC）——需要将气候系统模型与气候变化的经济和社会影响的表示联系起来，以及跨时间和空间的各种、不确定影响的聚合。越来越多的文献研究了支持 SCC 计算的模型的基本结构元素的影响。这项工作以零碎的方式积累起来，因此它们的相对重要性尚不清楚。在这里，我们对 SCC 的证据进行了全面综合，将 1,823 项研究中的 147 个 SCC 估计值与对这些研究作者的调查相结合。已发布的 2020 年 SCC 值分布广泛且基本右偏，显示出重右尾的证据（截断平均值为 132 美元）。方差分析揭示了包含持续损害、地球系统的表示和分布加权的重要作用。然而，我们的调查显示，专家认为，由于模型结构的采样不足、损害特征的描述不完整以及贴现率高，文献低估了 SCC。为了解决这种不平衡问题，我们根据文献中的变异训练了一个随机森林模型，并使用它来生成一个合成的 SCC 分布，该分布更接近于专家对适当模型结构和折扣的评估。这种合成分布在 2020 年脉冲年的平均价格为每吨 CO2 283 美元（5% 至 95% 范围：32 美元至 874 美元），高于大多数官方政府估计，包括美国环保署 2023 年的更新。