Reduced U.S. Methane Emissions during the COVID-19 Pandemic

Abstract

The coronavirus disease 2019 (COVID-19) pandemic disrupted normal human activities worldwide, and mobility reductions resulted in reduced levels of air pollutants and greenhouse gases emissions. Here, we examine the impact of these disruptions on a potent greenhouse gas, methane (CH4), over the U.S. In this study, we quantified CH4 emissions from the contiguous U.S. between 2019 and 2021 by analyzing inverse modeling results derived from atmospheric measurements made at 35 sites across the country. Our estimates indicate emission reductions of -2.5 (-3.2 to -2.1, 1) Tgy-1 CH4 in 2020 and -2.9 (-5.2 to -0.4) Tgy-1 in 2021, relative to 2019. The respective percentage change was a -4.3 (-5.1 to -3.5) % reduction in 2020 and -4.8 (-8.3 to -0.7) % in 2021, relative to 2019. Combining with process-based inventory emission datasets, we found that this reduction was primarily due to decreased fossil fuel and agricultural emissions; however, record-breaking forest fires resulted in an increase of 0.4 (0.1 to 0.8) Tgy⁻¹ in 2020-2019, equal to a 20 (2.9 to 46) % increase in CH4 emissions from the western U.S.