In cities in particular, the air is contaminated with pollutants. There have been many attempts to rid them of this - with questionable success.
The corona lockdowns meant reduced activity for many people - in their free time and professionally. Not so for atmospheric researchers, quite the opposite: the decline in traffic and industrial production presented them with a unique opportunity. They were able to measure how the reduced release of pollutants worldwide is affecting air purity. This was an acid test for the models and computer simulations that atmospheric chemists and physicists use to make predictions and politicians to make proposals
