What Are the Different Measures of Mobility Telling Us About Surface Transportation CO2 Emissions During the COVID‐19 Pandemic?. Issue 11 (1st June 2021)

• Record Type: Journal Article
• Authors: Gensheimer, Johannes; Turner, Alexander J.; Shekhar, Ankit; Wenzel, Adrian; Keutsch, Frank N.; Chen, Jia
• Is Part Of: Journal of geophysical research. Volume 126:Issue 11(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-06-01
• Subjects: Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2021JD034664
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: The COVID‐19 pandemic led to widespread reductions in mobility and induced observable changes in atmospheric emissions. Recent work has employed novel mobility data sets as a proxy for trace gas emissions from traffic by scaling CO2 emissions linearly with those near‐real‐time mobility data. Yet, there has been little work evaluating these emission numbers. Here, we systematically compare these mobility data sets to traffic data from local governments in seven diverse urban and national/state regions to characterize the magnitude of errors that result from using the mobility data. We observe differences in excess of 60% between these mobility data sets and local traffic data. We could not find a general functional relationship between the mobility data and traffic flow over all the regions and observe higher deviations from using such general relationships than the original data. Finally, we give an overview of the potential errors that come from estimating CO2 emissions using (mobility or traffic) activity data. Future work should be cautious while using these mobility metrics for emission estimates. Plain Language Summary: The government‐imposed mobility restrictions due to the COVID‐19 pandemic led to observable changes in our atmosphere. We identify traffic activity reductions in the range of 7%–22% in 2020 compared to that 2019 in seven diverse urban and national/state regions using traffic data from local governments. Previous studies investigating these observed changes used new data sets from tech companies that track user mobility as a proxy for traffic activity. However, our work identifies important shortcomings using these new mobility data sets to directly estimate emissions from traffic, with calculated estimated traffic activity errors larger than 60% (deviations between novel mobility data and governmental traffic flow data). Further, we could not find a simple functional relationship between these new mobility data sets and data from local governments on traffic flow, indicating that one should be cautious while using these mobility metrics to assess emissions. Key Points: Recent work used novel mobility data for assessing the impact of the COVID‐19 pandemic on traffic CO2 emissions. However, we observe errors in excess of 60% The relationship between mobility and traffic activity data could not be explained by a general relationship over all investigated regions