Reduced traffic during the COVID-19 lockdown was likely the primary driver behind reduced CO2 emissions in Salt Lake City (SLC), according to a new study led by University of Utah professors Derek Mallia and John Lin, published in the Journal of Geophysical Research – Atmospheres.
High-density measurements of CO2 were combined with a statistical model to estimate reductions in greenhouse gas emissions across SLC during the lockdown.
The paper reports on evidence of an observable decrease in anthropogenic CO2 emissions. The analysis used measurements from the Salt Lake area’s two CO2 networks–Utah Urban Carbon Dioxide Network (UUCON) and a CO2 instrument installed on a light-rail train car (TRAX) that traverses the Salt Lake Valley. Together, the two networks estimated CO2 concentrations across SLC. The results suggest that high-density CO2 monitoring networks could be used to track the decarbonization of cities.
Of the paper, titled “Can we detect urban-scale CO2 emission changes within medium-sized cities?” Mallia said, “This work demonstrates that mobile-based carbon monitoring networks, like the one deployed on Salt Lake City’s TRAX train, will be critical tools for tracking decarbonization efforts for cities across the globe.”
Given that over half of anthropogenic CO2 is emitted from urban areas, cities will play a pivotal role in future decarbonization efforts, and quantifying CO2 emissions at the city-scale will be important for determining whether cities are meeting CO2 decarbonization targets.
The research was funded by the National Oceanic and Atmospheric Administration’s Climate Program Office (CPO) as part of an air quality research initiative to track impacts of COVID-19 lockdowns & recovery on urban atmospheric composition. The research showed that CO2 emissions across SLC relative to 2019 were reduced by ~20% during the first COVID-19 lockdown and that the largest reductions in CO2 were likely driven by reduced traffic, especially in downtown SLC on the northern end of the Salt Lake Valley.
Unlike other cities used to investigate emission reductions during the COVID-19 lockdown, SLC is a medium-sized metropolitan area with a population just over 1 million people and emits an order of magnitude less CO2 relative to larger cities like Los Angeles, San Francisco, and Washington DC/Baltimore. Determining whether CO2 emissions reductions are traceable for smaller cities and metropolitan areas has been an outstanding question which this paper now addresses. The study is the first to demonstrate that CO2 emissions in medium/small cities can be measured.
“While no one wishes for a repeat of the COVID shutdown, it does illustrate the large leverage a shift in societal behavior has on reducing greenhouse emissions, whether from reduced traffic or the transition to electric vehicles,” said Lin.
Ultimately, the analysis carried out here suggests that inverse models, combined with stationary and mobile CO2 observations, can track modest emission reductions in medium-sized cities, and to some degree, geographically identify emission adjustments at the city-scale. According to the researchers, novel urban CO2 observation networks, like the TRAX network, combined with new satellite-based measurements approaches, will also play a key role towards monitoring decarbonization efforts in cities.
Other contributors to the paper include Logan Mitchell, Andres Eduardo Gonzalez Vidal, Dien Wu, and Lewis Kunik.. Read the full paper here.
By David Pace
Watch the cool video from Utah Educational Network about monitoring air quality in Salt Lake County along UTA TRAX lines below: