Air pollution is an invisible killer. As such, it is often an overlooked problem. And for scientists, an overlooked problem is a challenge in disguise. So it was for a team who have been experimenting with ways to visually represent what is happening to air quality in the world's cities. They've come up with a series of striking, colourful charts that track urban air since the industrial revolution to get a rounded perspective on the problem. And what we can see is that European metropolises have seen their air quality improve in the years since tougher emissions regulations started to come into force. Cities in Asia and Africa, meanwhile, are getting far, far worse.

As the authors warn: “while some parts of the world are breathing easier, others face an increasingly toxic environment.”

What’s it like to grow up as part of the global elite? A series of revealing interviews with students at one of the world’s most expensive schools in Switzerland sheds light on a largely closed world. These ultra rich teenagers “never fly commercial” and are predictably obsessed with consuming designer goods. But when the researchers who interviewed this group of students followed up five years later, they were surprised to find some changed perspectives on privilege, justice and what it means to live a meaningful existence.

We've translated an article that has been a smash hit with our French readers lately – and it's easy to see why. It is packed with advice on how to keep your brain in good shape after 60. The basic answer here is exercise, but there are certain forms, such as group sports and active video games which are highly recommended for those hoping to keep their grey matter functioning in later life.

This week we’re also asking why island wildlife always ends up looking the same and tracing the illegal trade in pangolins, rhino horns and more by digging out suspicious patent filings.