Title: Changes in Greenhouse Gas Emissions during the COVID-19 Pandemic

Abstract:

Climate change is one of the most pressing problems of the 21st century. The COVID-19 pandemic caused an unprecedented and widespread reduction of activities that are often associated with greenhouse gas emissions. Carbon dioxide (CO2) shows positive correlation with global warming and is an important marker used in monitoring the climate crisis. However, detecting changes in CO2 emissions is difficult due to variability in real-time atmospheric data as well as its long residence time. Due to this challenge, prior work by Le Quere et. al. [Nature Climate Change, 10, 7, (2020)] and Liu et. al. [arXiv:2004.13614, (2020)] quantified the change in CO2 during the pandemic using a “bottom-up” approach, using data on behavioral changes to extrapolate estimated changes in CO2. Our work employed a “top-down” approach, in which we leverage atmospheric nitrogen dioxide (NO2) as a proxy for CO2. Although NO2 is not a greenhouse gas, there exists a high degree of overlap between processes that emit CO2 and NO2.

We investigated daily NO2 emissions collected by the OMI/Aura satellite and observed a statistically significant drop in emissions from 2019 to 2020 across the 11 countries included in our analysis (which includes 9 of the top 10 carbon emitters). This drop is unprecedented in relation to changes from 2015 to 2019; while other years have shown decreases, none have been as large or widespread as from 2019 to 2020. We then assess correlation between the change in emissions with levels of lockdown to determine if these behavioral changes are able to help curb the looming climate crisis. Many countries had a negative correlation however we conclude that finer-grain resolution is necessary, as generalizing lockdown measures on a by-country basis is too coarse.