Sarofim Marcus C, Giordano Michael R
Climate Change Division, US Environmental Protection Agency, Washington, DC 20001, USA.
AAAS S&T Policy Fellow Hosted by the EPA Office of Atmospheric Programs, Washington, DC 20001, USA.
Earth Syst Dyn. 2018;9:1013-1024. doi: 10.5194/esd-2018-6.
The 100-year global warming potential (GWP) is the primary metric used to compare the climate impacts of emissions of different greenhouse gases (GHGs). The GWP relies on radiative forcing rather than damages, assumes constant future concentrations, and integrates over a timescale of 100 years without discounting; these choices lead to a metric that is transparent and simple to calculate, but have also been criticized. In this paper, we take a quantitative approach to evaluating the choice of time horizon, accounting for many of these complicating factors. By calculating an equivalent GWP timescale based on discounted damages resulting from CH and CO pulses, we show that a 100-year timescale is consistent with a discount rate of 3.3% (interquartile range of 2.7% to 4.1% in a sensitivity analysis). This range of discount rates is consistent with those often considered for climate impact analyses. With increasing discount rates, equivalent timescales decrease. We recognize the limitations of evaluating metrics by relying only on climate impact equivalencies without consideration of the economic and political implications of metric implementation.
百年全球变暖潜能值（GWP）是用于比较不同温室气体（GHG）排放对气候影响的主要指标。全球变暖潜能值依赖于辐射强迫而非损害，假设未来浓度恒定，并在100年的时间尺度上进行积分且不进行贴现；这些选择产生了一个透明且易于计算的指标，但也受到了批评。在本文中，我们采用定量方法来评估时间跨度的选择，同时考虑了许多这些复杂因素。通过根据甲烷（CH）和二氧化碳（CO₂）脉冲造成的贴现损害计算等效全球变暖潜能值时间尺度，我们表明100年的时间尺度与3.3%的贴现率一致（在敏感性分析中的四分位间距为2.7%至4.1%）。这个贴现率范围与气候影响分析中经常考虑的贴现率一致。随着贴现率的增加，等效时间尺度会减小。我们认识到仅依靠气候影响等效性来评估指标而不考虑指标实施的经济和政治影响的局限性。
