The COVID-19 coronavirus outbreak has caused widespread alarm, travel bans, and the quarantine of multiple cities across the world.

But there's also been an unexpected effect on the environment, in the form of a notable drop in nitrogen dioxide emissions levels across China.

Data collected from the Tropospheric Monitoring Instrument (TROPOMI) on ESA's Sentinel-5 satellite shows a significant drop of nitrogen dioxide – a gas mainly emitted by cars, trucks, power plants and some industrial plants - between January 1 and February 25.