Observing System Choice Can Minimize Interference of the Biosphere in Studies of Urban CO₂ Emissions

Abstract

Cities across the world have announced initiatives to reduce anthropogenic greenhouse gas (GHG) emissions to combat climate change (Mi et al., 2019;Ramaswami et al., 2021). CO 2 has been identified as the main GHG of concern as it is the primary GHG emitted through human activities and is the single largest driver of our changing climate. In the United States, urban areas contribute ∼40% of nationwide CO 2 emissions (Dodman, 2009;Gurney et al., 2021), so studying and assessing CO 2 profiles in urban areas, particularly their sources and sinks, can be critical to address climate concerns. Specifically, it can: (a) help inform climate policy by providing direct information on emissions and assessing whether implemented policies are having desired effects and (b) support fundamental carbon cycle research by constraining human inputs into the atmosphere to disentangle changes driven by anthropogenic emissions or biosphere dynamics.The biosphere acts both as a source (via respiration) and a sink (via photosynthesis) of CO 2 , and because of its potential significance to understanding urban CO 2 , a number of previous studies have emphasized the biosphere and the role it plays. Previous representations of urban domains, including via isotopic measurements (Miller et al., 2020) and tower observations coupled with emission inventories (Sargent et al., 2018) have suggested that the biosphere is a substantial contributor to observed CO 2 in urban domains (Gourdji et al., 2022;Hardiman