Working on a remote tropical island in the Atlantic might sound like some sort of romantic idyll - but trying to conduct scientific research on a windy, isolated volanic outcrop is no picnic, as Lucy Carpenter can attest! Lucy is an atmopsheric chemist and a Professor at the University of York, whose work has helped to transform understanding of how oceans shape the air above them. She was one of the founding scientists behind the Cape Verde Atmospheric Observatory, established on São Vicente in 2006 and now a key global monitoring site. Measurements made there helped overturn a long-standing assumption: ozone loss is not solely a human-made problem. Lucy and her colleagues showed that gases released by natural marine processes can trigger chemical reactions that destroy ozone - demonstrating that the sea is not simply a passive backdrop to climate change but an active participant; affecting aerosols, clouds and ultimately the climate itself. More recently Lucy's expertise has taken her into the policy arena, co-chairing the scientific assessment panel for the Montreal Protocol: the international agreement designed to protect the ozone layer. In conversation with Professor Jim Al-Khalili, Lucy discusses her journey from sampling ocean air to turning the tide of global environmental policy - and explains why her passion for duathlons could arguably be seen as an easier pastime than scientific research.

As recently as a few years ago, the idea of a self-administered injection that would deliver proven weight-loss results might have sounded fantastical. Today, these medications are a reality and a global phenomenon; hailed in many quarters as “miracle drugs" for their success in treating obesity and diabetes. They do this by replicating a gut hormone called GLP‑1, which tells the brain you’ve eaten enough and nudges the pancreas to release insulin; and this hormone was discovered and decoded thanks to years of work by today's guest. Jens Juul Holst is a Professor of Medical Physiology and Biomedical Sciences at the University of Copenhagen. His efforts laid the groundwork for today’s weight loss jabs, earning him a slew of high-profile accolades and awards. Now it seems they might not only have positive impacts on obesity and diabetes, but also other health issues... But alongside the big success comes some big questions: including concerns over side effects, weight regain post-treatment, the black market in such drugs, and their cost and accessibility. In a frank conversation with Professor Jim Al-Khalili, Jens address these issues and shares his hopes for the future of GLP-1-focused research.

“I shall largely speak of mice,” the paper begins “but my thoughts are on man.”

So begins a truly extraordinary scientific paper, and an equally extraordinary story.

“Death Squared: The Explosive Growth and Demise of a Mouse Population.” was published in 1973 by John Calhoun, and it detailed his increasingly bizarre research into the psychological effects of overcrowding. Over two decades he built a series of ‘rodent utopias’, where he could keep a population of rats or mice, meet all their basic food and shelter needs, but mess around with population levels. He wanted to see how they responded to having to live, cheek-by-tiny-jowl, with far more other rats than they were used to. And it wasn’t pretty. Social orders melted into chaos, rodents fought indiscriminately, or shut themselves away at the top of the enclosure. Mating orders collapsed, population numbers tanked, and eventually, every single rat was dead.

His work came at a prescient time. In the 60s and 70s, the exponentially expanding human population was a hot-button topic, and ‘population panic’ was in full swing. Alongside the expansion of cities, creeping urban sprawl, rising city-centre crime rates and 'urban sinks', there grew a concern that human living conditions were about to take an interminable dive. How would we live, with so many of us on earth? Calhoun’s work was leapt on by the press and public as a dire prediction of our own coming collapse. His rodent utopias became a subject of great interest among architects and city planners, psychologists and sociologists, and anyone fascinated by the human condition. But has his work been misunderstood?

50 years on, what lessons can we take from the work of a ground-breaking but often misunderstood scientist, in the face of a human population now exceeding 8 billion. Emily Knight explores his extraordinary work, its implications for humanity, and the possibility of a human utopia, that might not look anything like you expect.

Presented and Produced by Emily Knight in Cardiff