Policy-Relevant Assessment of Urban CO₂ Emissions

Abstract

Global fossil fuel carbon dioxide (FFCO 2) emissions will be dictated to a great degree by the trajectory of emissions from urban areas. Conventional methods to quantify urban FFCO 2 emissions typically rely on self-reported economic/energy activity data transformed into emissions via standard emission factors. However, uncertainties in these traditional methods pose a roadblock to implementation of effective mitigation strategies, independently monitor long-term trends, and assess policy outcomes. Here, we demonstrate the applicability of the integration of a dense network of greenhouse gas sensors with a science-driven building and street-scale FFCO 2 emissions estimation through the atmospheric CO 2 inversion process. Whole-city FFCO 2 emissions agree within 3% annually. Current self-reported inventory emissions for the city of Indianapolis are 35% lower than our optimal estimate, with significant differences across activity sectors. Differences remain, however, regarding the spatial distribution of sectoral FFCO 2 emissions, underconstrained despite the inclusion of coemitted species information.

The Influence of Near-field Fluxes on Seasonal Carbon Dioxide Enhancements: Results From the Indianapolis Flux Experiment (INFLUX)

“…Unfortunately, we were not able to use the flask measurements to decompose into biogenic and fossil fuel components of the mismatch because 1) the flasks were sampled when the winds were from the west/southwest, i.e., to a large extent, the wind directions ignored for this analysis, and 2) differing subset of towers for this analysis vs the flask availability. However, the inversion of these data, separately optimizing fossil fuel and biogenic CO2 emissions, (Lauvaux et al 2020) indicated very little adjustment to the fossil fuel CO2 emissions from Hestia, further corroborating that the biogenic model is a larger contributor to the model-data mismatch.…”

“…Our approach, using a measured background, means that the enhancements are quite dependent on the biogenic signal of the background towers, and the enhancements are not "anthropogenic" enhancements. In the next step, optimization of fluxes using an inversion (Lauvaux et al 2020), the biogenic portion is determined via either method of background determination.…”

“…Data from World Meteorological Organization surface stations within the model domain were assimilated to nudge the model to the observations. The transport fields were then coupled offline to the Lagrangian Particle Dispersion Model (Uliasz 1994;Lauvaux et al 2012;Lauvaux et al 2020) in backward mode.…”

“…Improvements in the biogenic model can minimize these differences. Additionally an inversion using CO2 and CO mole fractions can optimize both the fossil and the biogenic CO2 separately (Lauvaux et al 2020).…”

The influence of near-field fluxes on seasonal carbon dioxide enhancements: Results from the Indianapolis Flux Experiment (INFLUX)

“…Our approach, using a measured background, means that the enhancements are quite dependent on the biogenic signal of the background towers, and the enhancements are not "anthropogenic" enhancements. In the next step, optimization of fluxes using an inversion (Lauvaux et al 2020), the biogenic portion is determined via either method of background determination. While we have focused on the biogenic signal at the background towers, urban biogenic CO2 fluxes also change with season (Miller et al 2020).…”