New Zealand Life Cycle Management Centre, Massey University, Palmerston North 4442, New Zealand.
School of Agriculture and Environment, Massey University, Palmerston North 4442, New Zealand.
Environ Sci Technol. 2020 Apr 7;54(7):4515-4527. doi: 10.1021/acs.est.9b06991. Epub 2020 Mar 12.
Quantifying greenhouse gas (GHG) emissions and setting GHG emissions budgets for anthropogenic systems are influenced by several value and modeling choices. This study, for the first time, quantified the influence of choice of GHG accounting approach, GHG metric, time horizon, climate threshold, global emissions budget calculation method, and effort-sharing approach, taking New Zealand (NZ) as a case study. First, NZ's production- and consumption-based emissions were quantified using multiregional input-output analysis and applying different GHG metrics (global warming and temperature potentials) and time horizons (20 and 100 years). Second, global emissions budgets for 1.5 °C, 2 °C, and 1 W m climate thresholds were estimated. Budget shares were then assigned to NZ using two effort-sharing approaches (grandfathering and economic value), and emissions were benchmarked against the assigned shares. Finally, the analysis was undertaken at the NZ sector level. The results showed that, for each GHG accounting approach, NZ's total emissions exceeded their budget shares, irrespective of the choices; the largest source of uncertainty was the choice of global emissions budget calculation method, followed by GHG metric, climate threshold, effort-sharing approach, and reference year for the grandfathering approach. The sector-level analysis showed that, while most sectors exceeded their budget shares, some performed within them. The ranking of uncertainty sources was quite different at the sector level, with the choice of effort-sharing approach providing the largest source of uncertainty. Overall, the study indicates the importance of handling value and modeling choices in a transparent way when quantifying GHG emissions and setting emissions budgets for anthropogenic systems.
量化人为系统的温室气体 (GHG) 排放并为其设定 GHG 排放预算会受到多种价值和建模选择的影响。本研究首次通过以新西兰（NZ）为案例研究，量化了 GHG 核算方法、GHG 指标、时间范围、气候阈值、全球排放预算计算方法和分配方法的选择对人为系统的 GHG 排放和排放预算的影响。首先，使用多区域投入产出分析并应用不同的 GHG 指标（全球变暖潜势和温度潜势）和时间范围（20 年和 100 年）来量化 NZ 的生产和消费排放。其次，估算了 1.5°C、2°C 和 1 W m-2 气候阈值的全球排放预算。然后使用两种分配方法（祖父法和经济价值法）将预算份额分配给 NZ，并将排放与分配的份额进行基准测试。最后，在 NZ 部门层面进行了分析。结果表明，对于每种 GHG 核算方法，无论选择如何，NZ 的总排放量均超过其预算份额；最大的不确定性来源是全球排放预算计算方法的选择，其次是 GHG 指标、气候阈值、分配方法和祖父法的参考年。部门层面的分析表明，尽管大多数部门的排放量超过了预算份额，但也有一些部门在预算内。不确定性来源的排名在部门层面上有很大差异，分配方法的选择是最大的不确定性来源。总体而言，该研究表明在量化人为系统的 GHG 排放和设定排放预算时，以透明的方式处理价值和建模选择非常重要。
