Coronavirus: Air pollution and CO2 fall rapidly as virus spreads
"Levels of air pollutants and warming gases over some cities and regions are showing significant drops as coronavirus impacts work and travel.
Researchers in New York told the BBC their early results showed carbon monoxide mainly from cars had been reduced by nearly 50% compared with last year.
Emissions of the planet-heating gas CO2 have also fallen sharply.
But there are warnings levels could rise rapidly after the pandemic."