基于多源证据估算气候敏感度最新研究进展:IPCC AR6解读

Advances in the assessment of climate sensitivity based on multi-source evidence:interpreting IPCC AR6

本文依据政府间气候变化专门委员会(IPCC)第六次评估报告(AR6)第一工作组(WGI)报告第七章的内容,详细解读了基于多源证据对气候敏感度的估算,这些证据包括:过程理解、仪器记录、古气候数据和萌现约束。得到的结论是,多源证据支持平衡态气候敏感度(ECS)的中心估计值接近3℃,可能区间为2.5~4.0℃,非常可能区间为2.0~5.0℃;瞬态气候响应(TCR)的最佳估值为1.8℃,可能区间为1.4~2.2℃,非常可能区间为1.2~2.4℃。与之前历次IPCC评估报告相比,AR6关于气候敏感度的估算最为重要的创新之处为,它没有将气候模式结果当作唯一证据,而是仅仅给出第六次国际耦合模式比较计划(CMIP6)结果并与基于多源证据的综合评估结果进行了对比。通过对比发现,CMIP6关于ECS与TCR的平均值均高于第五次国际耦合模式比较计划(CMIP5)和AR6的综合评估结果。相比CMIP6,AR6综合了多个证据线有效地缩小了ECS的不确定范围。

Based on the Chapter seven from the Sixth Assessment Report(AR6)contributed by the Intergovernmental Panel on Climate Change(IPCC)Working Group I(WGI),this study interprets the assessment of climate sensitivity from multi-source evidence,including process understanding,instrumental records,paleoclimate data,and emergent constraints.The conclusion is that this evidence gives a combined best estimate of 3℃to equilibrium climate sensitivity(ECS),with a likely range of 2.5—4.0℃and a very likely range of 2.0—5.0℃.Meanwhile,for transient climate response(TCR)the best estimate is 1.8℃,with a likely range of 1.4—2.2℃and a very likely range of 1.2—2.4℃.Compared with previous IPCC reports,the most important innovations in AR6 regarding the estimation of climate sensitivity are that Earth climate system models were not considered as a line of evidence,and that the CMIP6 results were only given for comparison with the combined estimate from other evidence.The average ECS and TCR from CMIP6 were higher than those in CMIP5 and the best estimates in AR6,and the uncertainty range of ECS based on multi-source evidence was effectively narrowed compared with that based on CMIP6.