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Pledges to reduce greenhouse gas emissions are largely unachievable says a major audit of commitments to the Paris Climate Accord. Air pollution in Delhi is so bad, breathing the toxic particles has been likened to smoking. Can a scientific assessment of the multiple causes help provide a way forward? We examine a new way of making new plastic – from old plastic. And why sending some stem cells to the international space station might help astronauts travel further.
We’re all familiar with the sensation of sleepiness – heavy eye-lid, that warm, fuzzy feeling. But, one listener wants to know, what’s actually going on in our body and brain when tiredness takes over?

We investigate how our psycho-motor skills are affected by fatigue in a driving simulator. And we ask how does sleepiness change with age? Why, when tired, do adults crave a nap but children become ever more excitable? And what the hell’s going on with teenagers? We have some answers.

(Image: Tourists wearing masks to protect themselves from smog in New Delhi, India. Credit: Sushil Kumar/Hindustan Times via Getty Images)