Work

COVID-19 impacts on anthropogenic NO x emissions in China, the contiguous U.S., and Europe: insights from joint TROPOMI and surface NO 2 data assimilation

Year: 2026

Type: article

Abstract: This study integrates satellite and surface NO 2 measurements through the ensemble square root filter and the GEOS‐Chem model to estimate anthropogenic NO x emissions for China, the contiguous U.S., and Europe over 2019–2020, and further examines how the COVID‐19 pandemic altered emission patterns and sectoral contributions. Our results show that in 2020, anthropogenic NO x emissions were 19.20 ± 5.87 Tg in China, 8.96 ± 2.90 Tg in the contiguous U.S., and 10.56 ± 2.95 Tg in Europe. Compared with 2019, emissions decreased by about 5.38% in China, 8.94% in the contiguous U.S., and 15.38% in Europe. In China, emission reductions came from transportation, power plants, and industry. In contrast, reductions in the contiguous U.S. and Europe were almost entirely from transportation. These differences reflect the fundamental gap in energy structure and industry models between developed and developing economies. During the first wave of the pandemic, emissions fell sharply compared to the same period in 2019. The decreases were 18.04% in China, 10.56% in the contiguous U.S., and 21.74% in Europe. Large spatial variations were observed within each region. This work provides observation-based evidence of NO x emission changes across major world regions during COVID 19. It highlights how emissions can behave differently under sudden public health crises. The findings are useful for checking bottom-up emission inventories, assessing extreme events’ impacts on air quality, and designing better emission reduction policies.

Source: Environmental Research Letters

DOI: 10.1088/1748-9326/aeaf6b