What are different measures of mobility changes telling us about
emission reductions during the COVID-19 pandemic?
The COVID-19 pandemic led to widespread reductions in mobility and
induced observable changes in the atmosphere. Recent work has employed
novel mobility datasets as a proxy for trace gas emissions from traffic,
yet there has been little work evaluating these emission numbers. Here,
we systematically compare these mobility datasets to traffic data from
local governments in seven diverse urban and rural regions to
characterize the magnitude of errors in emissions that result from using
the mobility data. We observe differences in excess of 60% between
these mobility datasets and local traffic data, which result in large
errors in emission estimates. We could not find a general functional
relationship between mobility data and traffic flow over all regions.
Future work should be cautious when using these mobility metrics for
emission estimates. Further, we use the local government data to
identify emission reductions from traffic in the range of 7-22% in 2020
compared to 2019.