Many studies project that climate change can cause a significant number of excess deaths. Yet, in integrated assessment models (IAMs) that determine the social cost of carbon (SCC) and prescribe optimal climate policy, human mortality impacts are limited and not updated to the latest scientific understanding. This study extends the DICE-2016 IAM to explicitly include temperature-related mortality impacts by estimating a climate-mortality damage function. We introduce a metric, the mortality cost of carbon (MCC), that estimates the number of deaths caused by the emissions of one additional metric ton of CO2. In the baseline emissions scenario, the 2020 MCC is 2.26 × 10^‒4 [low to high estimate −1.71× 10^‒4 to 6.78 × 10^‒4] excess deaths per metric ton of 2020 emissions. This implies that adding 4,434 metric tons of carbon dioxide in 2020—equivalent to the lifetime emissions of 3.5 average Americans—causes one excess death globally in expectation between 2020-2100. Incorporating mortality costs increases the 2020 SCC from $37 to $258 [−$69 to $545] per metric ton in the baseline emissions scenario. Optimal climate policy changes from gradual emissions reductions starting in 2050 to full decarbonization by 2050 when mortality is considered.

许多研究预测气候变化可能导致大量死亡。然而，在确定碳的社会成本（SCC）并制定最佳气候政策的综合评估模型（IAM）中，人类死亡率的影响是有限的，并且没有更新到最新的科学认识。这项研究扩展了 DICE-2016 IAM，通过估计气候死亡率损害函数，明确包括与温度相关的死亡率影响。我们引入了一个指标，即碳的死亡率成本 (MCC)，该指标可估计因额外排放一吨二氧化碳而导致的死亡人数。在基准排放情景中，2020 年 MCC 为每公吨 2020 年排放量 2.26 × 10 ⁻⁴ [从低到高估计值 -1.71× 10 ⁻⁴至 6.78 × 10 ⁻⁴ ] 超额死亡人数。这意味着，2020 年二氧化碳排放量将增加 4,434 吨（相当于 3.5 个美国人平均一生的排放量），预计 2020 年至 2100 年期间将导致全球超额死亡 1 人。在基准排放情景中，纳入死亡率成本后，2020 年 SCC 从每公吨 37 美元增加到 258 美元[−69 美元到 545 美元]。最佳气候政策从 2050 年开始逐步减排转变为到 2050 年考虑死亡率时完全脱碳。