Pandemic lockdowns show how to clear the air

Frederik Noack and his colleagues spent spring 2020 working at home as governments worldwide instituted lockdowns in response to the COVID-19 pandemic. Although the environmental economists initially joked that they were helping to save the world from their couches, as air pollution plunged in cities devoid of traffic and industrial activity, Noack quickly realized that lockdowns represented "a unique natural experiment to study the effects of economic activities on air pollution". The response was not uniform, however. Whereas smog was greatly reduced over large swaths of North America, Europe, and East Asia, areas where air pollution is generated primarily from traffic and industrial activities, pollution levels stayed the same or even increased in the American Midwest, parts of Africa, Latin America, and southern Europe.