Guidance on emissions metrics for nationally determined contributions under the Paris Agreement
Guidance on emissions metrics for nationally determined contributions under the Paris Agreement
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DOI：
10.1088/1748-9326/ab4df4
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发表时间：
2019-12-01
影响因子：
6.7
通讯作者：
Smith, Christopher J.
中科院分区：
文献类型：
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作者：
Denison, Steve;Forster, Piers M.;Smith, Christopher J.
《巴黎协定》下的许多国家自主贡献（NDCs）遵循以二氧化碳当量吨为单位指定排放水平的既定做法。全球变暖潜能值（GWP）是最常用于汇总不同温室气体（ghg）贡献的排放度量。然而，已知以这种方式表达的途径对气候的影响是模糊的。出于这个原因，有人提出了替代方案，但在《巴黎协定》的背景下，这种模糊性没有得到量化。在这里，我们使用与将温度上升限制在远低于2摄氏度的目标相一致的路径来评估温度变化。这些路径取自IPCC关于全球变暖1.5摄氏度的特别报告（SR15）。对二氧化碳排放水平进行调整，以便在给定的排放指标下，所有途径都具有相同的二氧化碳当量排放总量，但具有不同比例的短期和长期污染物。我们表明，当使用GWP（100）时，这种差异对预估的影响高达0.17℃。减少这种模糊性的办法包括使用不同的排放指标或在国家自主贡献中增加关于个别温室气体排放水平的补充信息。我们建议采用后者，因为它简单，而且不需要就使用不同的排放度量标准达成一致。
Many nationally determined contributions (NDCs) under the Paris Agreement follow the established practice of specifying emissions levels in tonnes of CO2 equivalent emissions. The Global Warming Potential (GWP) is the emissions metric used most often to aggregate contributions from different greenhouse gases (GHGs). However, the climate impact of pathways expressed in this way is known to be ambiguous. For this reason, alternatives have been proposed but the ambiguity has not been quantified in the context of the Paris Agreement. Here we assess the variation in temperature using pathways consistent with the ambition of limiting temperature increases to well below 2 C. These are taken from the IPCC Special Report on Global Warming of 1.5 C (SR15). The CO2 emission levels are adjusted so that the pathways all have the same total CO2 equivalent emissions for a given emissions metric but have different proportions of short-lived and long-lived pollutants. We show that this difference affects projections by up to 0.17 C when GWP(100) is used. Options of reducing this ambiguity include using a different emissions metric or adding supplementary information in NDCs about the emissions levels of individual GHGs. We suggest the latter on the grounds of simplicity and because it does not require agreement on the use of a different emissions metric.