Ahn D Y, Goldberg D L, Coombes Toby, Kleiman Gary, Anenberg S C
Milken School of Public Health, George Washington University, Washington, DC, United States of America.
C40 Cities Climate Leadership Group Inc., New York, NY, United States of America.
Environ Res Lett. 2023 Mar 1;18(3):034032. doi: 10.1088/1748-9326/acbb91. Epub 2023 Feb 28.
Under the leadership of the C40 Cities Climate Leadership Group (C40), approximately 1100 global cities have signed to reach net-zero emissions by 2050. Accurate greenhouse gas emission calculations at the city-scale have become critical. This study forms a bridge between the two emission calculation methods: (a) the city-scale accounting used by C40 cities-the Global Protocol for Community-Scale Greenhouse Gas Emission Inventories (GPC) and (b) the global-scale gridded datasets used by the research community-the Emission Database for Global Atmospheric Research (EDGAR) and Open-Source Data Inventory for Anthropogenic CO (ODIAC). For the emission magnitudes of 78 C40 cities, we find good correlations between the GPC and EDGAR ( = 0.80) and the GPC and ODIAC ( = 0.72). Regionally, African cities show the largest variability in the three emission estimates. For the emission trends, the standard deviation of the differences is ±4.7% yr for EDGAR vs. GPC and is ±3.9% yr for ODIAC vs. GPC: a factor of ∼2 larger than the trends that many C40 cities pledged (net-zero by 2050 from 2010, or -2.5% yr). To examine the source of discrepancies in the emission datasets, we assess the impact of spatial resolutions of EDGAR (0.1°) and ODIAC (1 km) on estimating varying-sized cities' emissions. Our analysis shows that the coarser resolution of EDGAR can artificially decrease emissions by 13% for cities smaller than 1000 km. We find that data quality of emission factors (EFs) used in GPC inventories vary regionally: the highest quality for European and North American and the lowest for African and Latin American cities. Our study indicates that the following items should be prioritized to reduce the discrepancies between the two emission calculation methods: (a) implementing local-specific/up-to-date EFs in GPC inventories, (b) keeping the global power plant database current, and (c) incorporating satellite-derived CO datasets (i.e. NASA OCO-3).
在C40城市气候领导集团（C40）的领导下，约1100个全球城市已签署协议，到2050年实现净零排放。城市尺度上准确的温室气体排放计算变得至关重要。本研究在两种排放计算方法之间架起了一座桥梁：（a）C40城市使用的城市尺度核算方法——《社区尺度温室气体排放清单全球议定书》（GPC），以及（b）研究界使用的全球尺度网格化数据集——《全球大气研究排放数据库》（EDGAR）和《人为一氧化碳开源数据清单》（ODIAC）。对于78个C40城市的排放规模，我们发现GPC与EDGAR之间（=0.80）以及GPC与ODIAC之间（=0.72）存在良好的相关性。在区域上，非洲城市在这三种排放估算中显示出最大的变异性。对于排放趋势，EDGAR与GPC相比差异的标准差为±4.7%/年，ODIAC与GPC相比为±3.9%/年：约为许多C40城市承诺的趋势（从2010年到2050年净零排放，即-2.5%/年）的两倍。为了研究排放数据集中差异的来源，我们评估了EDGAR（0.1°）和ODIAC（1公里）的空间分辨率对不同规模城市排放估算的影响。我们的分析表明，对于面积小于1000平方公里的城市，EDGAR较粗的分辨率会人为地使排放量减少13%。我们发现GPC清单中使用的排放因子（EFs）的数据质量因地区而异：欧洲和北美地区质量最高，非洲和拉丁美洲城市质量最低。我们的研究表明，为减少两种排放计算方法之间的差异，应优先考虑以下事项：（a）在GPC清单中采用针对当地的/最新的排放因子，（b）使全球发电厂数据库保持最新，以及（c）纳入卫星衍生的一氧化碳数据集（即美国国家航空航天局的OCO-3）。
