This is what pollution looks like on a European scale.
The animation shows the concentration and movement through the atmosphere of nitrogen dioxide.
NO₂ is a problem gas that is produced primarily by vehicle exhausts and industrial activity via the burning of fossil fuels.
The map covers a sample period from 5 to 10 January, and describes the behaviour of NO₂ at ground level on an hourly basis.
The worst air quality peaks in the white.
This fascinating insight was produced for the BBC by the Copernicus Atmosphere Monitoring Service (CAMS), which is based at the European Centre for Medium-Range Weather Forecasts (ECMWF) in Reading.
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To make this type of animation, CAMS incorporates satellite observations and surface measurements.
But as extensive as these data-sets have now become, they don’t give a complete, real-time picture.
So, the scientists must also marry the sensor information with models – of how the atmosphere moves and what the weather is doing.
One of the first things you’ll notice in the animation is the prevalence of NO₂ emanating from the “usual suspects”.
“What you immediately see are the larger cities. You see Madrid, you see Paris, you see Moscow, you see London,” explains Richard Engelen, the deputy head of CAMS.
“Then you’ll see more industrial areas, like Germany but also in the UK. You’ll see too those areas where there are very dense traffic infrastructures, such as the Netherlands and Belgium where you have a lot of traffic from the two main ports at Rotterdam and Antwerp. These are the emission sources that always pop up,” he told BBC News.