A Comparative Analysis of Anthropogenic CO2 Emissions at City Level Using OCO‐2 Observations: A Global Perspective. Issue 9 (4th September 2019) - Fu, Peng
Abstract: Satellite observations of anthropogenic carbon dioxide (CO2 ) emissions within urban settings offer unique potential to understand carbon sources and sinks and evaluate carbon mitigation strategies. Despite availability of column‐averaged dry air mole fraction of CO2 ( X CO 2 ) from Orbiting Carbon Observatory‐2 (OCO‐2), temporal variations of X CO 2 and their drivers in cities remain poorly understood due to inconsistent definitions of urban extent, diverse urban forms, and unresolved impacts of urban vegetation on carbon fluxes. To this end, this study revealed that OCO‐2 X CO 2 measurements from 2014 to 2018 exhibited statistically significant seasonal and trend components for each city. A correlation analysis suggested a weak association between X CO 2 trends and fossil fuel CO2 emissions ( FF CO 2 ) trends but a close relationship between yearly average X CO 2 and FF CO 2 trends. Vegetation abundance exhibited a negative relationship with the X CO 2 seasonality, though it only explained 21% of the variance. No statistically significant relationship between urban morphological factors (areal extent, complexity, and compactness) and temporal X CO 2 components was observed. However, urban morphological factors had a close relationship with the total amount of FF CO 2 aggregated over the study period. Thus, it was speculated that urban morphological factors exerted their influence on X CO 2 through fossil fuel consumption. When only cities of high normalized difference vegetation index seasonality were used, statistically significant correlation coefficients between urban morphological factors and winter/summer averaged X CO 2 measurements were found. The variations of these correlation coefficients between leaf‐on and leaf‐off seasons stress the important role that urban trees play in mitigating carbon emissions in cities. Key Points: X CO 2 variation is associated with fossil fuel CO2 emission, vegetation abundance, and urban form Fossil fuel CO2 emissions are highly related to urban morphological factors Trees (or vegetation) play an important role in mitigating CO2 emissions in cities