China's COVID-19 interventions caused abrupt decline in tropospheric nitrogen dioxide

Pandemics and the Environment: China's COVID-19 Interventions Reduced Nitrogen Dioxide Levels A new Special Collection of Science Advances papers will delve into how pandemics such as COVID-19 affect - and are affected by - global environmental conditions, underscoring the interconnectedness of global processes.

"Economic lockdowns this year, designed to slow the spread of COVID-19, have been like pressing the pause button on environmental degradation and the resulting reductions in air and water pollution are dramatic," writes Kip Hodges and Jeremy Jackson in an Editorial that introduces the Special Collection. "Such trends remind us of how much our actions drive environmental quality and just how badly we have behaved as stewards of our planet."

They emphasize that heavy investment in green energy, broader research perspectives, and widespread commitment to policy decisions that support the findings of scientific research will be crucial to achieving a more sustainable Earth.

In the first research paper of this Special Collection, an analysis of the environmental impact of China's COVID-19 policy interventions relied on satellite measurements to identify an average 48% drop in nitrogen dioxide densities over China from 20 days before to 20 days after the Lunar New Year on January 25, 2020. While this greenhouse gas - an indicator of fossil fuel consumption - typically decreases during the holiday, when traffic slows and most Chinese factories close, Fei Liu and colleagues observed that the reduction was about 21% greater than in 2015 through 2019.

Fei Liu and colleagues conclude that this enhanced nitrogen dioxide reduction correlated to government announcements of the first reported COVID-19 case in each province and to the initiation of lockdowns, which further subdued both travel and business activity. The researchers monitored shifts in atmospheric nitrogen oxide (which can reflect changes in fossil fuel combustion in a matter of hours) over China using the Dutch-Finnish Ozone Monitoring Instrument (OMI) on board a NASA satellite launched in 2004, and the instrument's successor, the Tropospheric Monitoring Instrument (TROPOMI), which offers measurements with higher spatial resolution from its perch aboard an ESA satellite launched in 2017. Their findings suggest that the tropospheric vertical column density of nitrogen oxide dropped once after the government publicly reported the first COVID-19 case in each province, then dropped again after lockdowns were implemented. "While temporary, these substantial reductions in air pollution may have positive health impact for lives in otherwise heavily polluted areas," the authors write. "This unusual period offers a rare counterfactual of a potential society which uses substantially less fossil fuels and has lower mobility."