Explore every episode of the podcast Science Weekly

Madeleine Finlay hears from Steve Ramirez, an associate professor of psychological and brain sciences at Boston University, whose book How to Change a Memory was shortlisted for this year’s Royal Society Trivedi science book prize. He explains how scientists have been able to locate memories in the brains of rodents, trigger them artificially and even remove them, and reveals what the practical applications of this science could one day be for humans.. Help support our independent journalism at theguardian.com/sciencepod

Our use of cleaning products has increased since the pandemic, but do we understand what they could be doing to our health? The journalist Rebecca Seal recently wrote for the Guardian about the potential impacts of the many chemicals we now use in our homes. She tells Madeleine Finlay how social media has also played a role in transforming our cleaning habits, why the impact of indoor air pollution is so hard to study, and what the current evidence is that cleaning products may be causing harm. Help support our independent journalism at theguardian.com/sciencepod

Madeleine Finlay sits down with her co-host and Guardian science editor, Ian Sample, to discuss three science stories from the week, including a study that offers a clue in the age-old debate about whether sex differences are present from birth or a product of socialisation. Also on the agenda is the super El Niño, which is predicted to lead to 450,000 deaths in the next six months, and an answer to why the UK’s meningitis outbreak earlier this year was so big.. Help support our independent journalism at theguardian.com/sciencepod

As diet trends proliferate on social media, it can be hard to work out which are backed by science and which should be ignored. From paleo to keto, raw food to intermittent fasting, each attracts a tribe of ardent followers. Now Daniel Lieberman, professor of biological sciences at Harvard University, has written a book to try to cut through the noise. In Fed Up, he uses his background as an evolutionary anthropologist to scrutinise the evidence, turning himself into a guinea pig in the process and trying various diets. In this podcast, he tells Ian Sample which one has remained part of his routine. Help support our independent journalism at theguardian.com/sciencepod

In early September, OpenAI announced it had solved a major mathematics problem that has stumped humans for nearly a century. The news left mathematicians reeling, and many expressed concern over what will be left for humans as AI becomes ever more adept at unravelling complex problems. Now 25 recipients of the Fields medal – often called the Nobel prize for maths – have signed an open letter expressing their fears of a ‘severe misalignment’ between AI companies and their field. To find out how AI is likely to upend maths – and how mathematicians might respond – Ian Sample speaks to Colva Roney-Dougal, professor of pure mathematics at the University of St Andrews. Help support our independent journalism at theguardian.com/sciencepod

Collagen powders, gummies and pills have boomed in popularity in recent years boosted by claims that they smooth wrinkles, promote glossy hair and help with joint pain. Amid the noise it can be hard to figure out whether there’s any actual science behind the promise of looking younger for longer. Luckily Dr Xand van Tulleken has spent the past three years writing Make me well: a quest to understand the confusing world of wellness, and his chapter on collagen dives deep into the evidence. He tells Madeleine Finlay what collagen does in the body, how we can get it without splashing out on expensive supplements, and why getting to the truth behind wellness claims can be so hard. Help support our independent journalism at theguardian.com/sciencepod

In this episode of Science Weekly, recorded in front of an audience at the London podcast festival on 3 September, Ian Sample hears from Michael Safi, the host of the Guardian’s chart-topping podcast about artificial intelligence, Black Box. In series two, Black Box: the chatbots, Michael meets people who have become convinced they have made scientific breakthroughs, cured diseases or invented new technologies using AI chatbots. Ian, Michael and Science Weekly’s co-host Madeleine Finlay explore the phenomenon labelled ‘AI psychosis’ and ask what it reveals about a technology now used by more than a billion people. Help support our independent journalism at theguardian.com/sciencepod

For decades physicists have been puzzling over the enigma of dark matter. We think it makes up 85% of the matter in the universe, but the mysterious substance cannot be seen or detected, and we know about it mainly through observations of the gravitational effects it has on other things. But now scientists believe they may be a step closer to detecting it. Science editor Ian Sample explains to Madeleine Finlay why, if confirmed, the finding could completely transform our understanding of the universe. And Dr Samuel Eriksen, senior research associate at the University of Bristol, and first author of the research paper, explains how the finding has been received in the physics community. Help support our independent journalism at theguardian.com/sciencepod

Who’s more likely to steal sweets from a child? According to science, it’s the rich. A study seemingly confirming our suspicions about the moral behaviour of the wealthy was one of the winners of the 2026 Ig Nobel prizes, which honour research that makes you laugh and then think. Science editor Ian Sample tells Madeleine Finlay what the researchers think could be behind the phenomenon, and they explore some of the other awards, including one for a surprising quality we look for in our friends and another for a biomechanical definition of kissing. Help support our independent journalism at theguardian.com/sciencepod

From the Guardian Investigates team: Across the world, hundreds of people have come to believe they have made extraordinary scientific discoveries with AI chatbots such as ChatGPT, Claude and Gemini. Others say their AI has ‘awakened’ or is leading them to a higher spiritual realm. The Guardian journalist Michael Safi begins investigating a phenomenon labelled ‘AI psychosis’, travelling to the US to meet two people who have been on weird journeys with their chatbots. Help support our independent journalism at theguardian.com/sciencepod

Methane is a potent greenhouse gas that traps more than 80 times as much heat than carbon dioxide over a 20-year period and causes 25% of global heating today. We definitely don’t want this gas spewing needlessly into the atmosphere, but in 2023 that’s exactly what environment editor Damian Carrington found was happening when he reported on 1,000 super-emitting methane leaks across the globe. Now Turkmenistan, the worst country for mega-leaks, has begun to plug them. Damian tells Madeleine Finlay why some experts call stopping leaks the climate ‘emergency brake’ and reveals which countries are still failing to act. Help support our independent journalism at theguardian.com/sciencepod

Ever since the earliest known recording of whale song was made in 1949, researchers have been captivated by the wails, rumbles, clicks, grunts and squeals of their communication. As technology improves, scientists are decoding the intricate patterns that make different species’ vocalisations distinctive. Madeleine Finlay hears from Emma Bryce, a journalist who has spent months investigating human efforts to understand whale song. She explains how this knowledge could help us better protect whales from human-made harms. Credits: 1. Copyright 1978 National Geographic Society and 1977 Capitol Records, Inc. Commentary by Dr Roger Payne 2. Valeria Vergara/Raincoast Conservation Foundation 3. Footage courtesy of Raincoast Conservation Foundation - Obtained for research under SARA permit XMMS 4 2026 4. Video by Amanda Cotton/Project CETI 5. Footage courtesy of Valeria Vergara and GREMM. Obtained for research under SARA permits QUE-MM02-2016 and QUE-LEP-001-2018 6. Project CETI 7. Project CETI. Help support our independent journalism at theguardian.com/sciencepod

AI companies have promised us world-shifting technology. But there’s a cost: loud, unsightly datacentres that drain environmental resources. As the government pushes their rapid growth, can local communities do anything to push back? Madeleine Finlay speaks to the Guardian’s global technology reporter Aisha Down about the backlash to datacentres across the UK and around the world. Help support our independent journalism at theguardian.com/sciencepod

Creatine has become the go-to supplement for anyone wanting to give their fitness a boost and build muscle. It’s even made it out of the gym, with influencers touting its cognitive benefits. But what’s the science behind creatine, and does the evidence stack up? Madeleine Finlay hears from science editor Ian Sample and Dr Justin Roberts, professor of nutritional physiology at Anglia Ruskin University. Help support our independent journalism at theguardian.com/sciencepod

After a summer that has seen England and Wales experience the driest July since records began, rain is finally on the horizon. But with reservoirs at ‘exceptionally low’ levels, will there be enough rain to replenish stocks? Madeleine Finlay hears from Dr Anna Murgatroyd, a lecturer in hydrology at Newcastle University, about how much rain we need to see us through next summer, why we’re now at increased risk of floods, and what we can all be doing to take better care of our water supplies. Help support our independent journalism at theguardian.com/sciencepod

One of the UK’s best fossil collections has been sold overseas in what experts have called a loss to the nation. The collection, which is now on display at the Natural History Museum in Abu Dhabi, was gathered on Dorset’s Jurassic Coast. As dinosaur fossils sell to private collectors for increasingly large sums, scientists are worried that domestic museums are being priced out of the market, and in turn scientists are missing out on the opportunity to make new observations. To find out how fossils became big business and what it could mean for research, Madeleine Finlay hears from science correspondent Nicola Davis. Help support our independent journalism at theguardian.com/sciencepod

Each year the Guardian runs a competition to find the invertebrate of the year. To find out more about the 2026 nominees science editor Ian Sample hears from climate reporter Petra Stock, environment reporter Oliver Milman and Science Weekly co-host Madeleine Finlay. They each nominate an incredible invertebrate that you might never have heard of, and argue why their choice should be crowned the winner. Vote for your favourite now and the winner will be crowned on 17 August. Help support our independent journalism at theguardian.com/sciencepod

Books have never been trendier, but studies show that as more and more things compete for our frazzled attention spans, we’re reading less and less. This is a problem because reading has a wealth of cognitive benefits that we’re in danger of missing out on. To find out why declining literacy could affect everything from memory to IQ, Madeleine Finlay speaks to the Guardian’s science editor, Ian Sample. She also hears from Prof Falk Huettig, an experimental psychologist at the Max Planck Institute for Psycholinguistics and author of The Perks of Being a Bookworm. Help support our independent journalism at theguardian.com/sciencepod

Madeleine Finlay is joined by Ian Sample, Guardian science editor, to discuss three eye-catching science stories including an investigation that has identified four distinct types of thinker. Also on the agenda is the unprecedented cyclosporiasis outbreak in the US which has now been linked to two fatalities, and the funding cuts that threaten the iconic Jodrell Bank world heritage site, home to the Lovell telescope. Help support our independent journalism at theguardian.com/sciencepod

Madeleine Finlay travels to the Rothbury estate in Northumberland, in north-east England. It’s a piece of land that has been in the same family for 700 years, but now it has been put up for sale and the UK’s Wildlife Trusts are trying to raise £30m to secure it intact. To find out what makes the area so special, Madeleine speaks to Katy Barke, the head of nature recovery for Northumberland Wildlife Trust. She also hears from Sam Turner, a professor of archaeology at Newcastle University, who is trying to work out how the land has been used across the centuries. This work will inform the strategy for nature recovery on the site. And Rosie Pearce, a farm liaison officer, explains how the project could bring more wildlife-friendly farming practices to the estate. Help support our independent journalism at theguardian.com/sciencepod

Saunas and cold plunge pools are popping up everywhere in the UK, bringing fiery heat and icy cold to a beach, city farm or park near you. Their users will be ready with all the reasons why it’s good for both the mind and the body. But what’s the evidence for the benefits of sauna and cold plunge? In this episode from April, Madeleine Finlay hears from Ian Sample and Dr Heather Massey, associate professor at the University of Portsmouth’s extreme environments laboratory. Help support our independent journalism at theguardian.com/sciencepod

In this episode from January 2026, Ian Sample puts listeners’ questions about dreams and nightmares to Dr Michelle Carr, the director of the Dream Engineering Laboratory in Montreal’s Centre for Advanced Research in Sleep Medicine, and the author of the book Into the Dream Lab. They look at why we dream, what we can learn by examining our dreams, and what we can do when dreams turn into nightmares. Carr gives her top tips for taking charge of our dreams and trying to influence their content. Help support our independent journalism at theguardian.com/sciencepod

Science correspondent Nicola Davis investigates the strange story of Tam O’Braan and his attempts to grow tea in Scotland. In episode three of this mini-series first broadcast in October 2025, all of O’Braan’s lies come to a head and it is revealed where he was sourcing the tea being supplied to hotels and shops. At trial, O’Braan takes the stand and the Scottish growers finally get some answers. But what remains today of the Scottish tea industry that O’Braan instigated?. Help support our independent journalism at theguardian.com/sciencepod

Science correspondent Nicola Davis investigates the strange story of Tam O’Braan and his attempts to grow tea in Scotland. In episode two of this mini-series first broadcast in October 2025, Nicola hears how O’Braan’s network of Scottish tea growers began to have suspicions about exactly what he was selling and where it came from, and how cutting-edge science helped provide some answers. Help support our independent journalism at theguardian.com/sciencepod

Science correspondent Nicola Davis investigates the strange story of Tam O’Braan and his attempts to grow tea in Scotland. In episode one of this mini-series first broadcast in October 2025, Nicola looks back on her first meeting with O’Braan while working on a feature about tea plantations in the UK. He was selling his award-winning Scottish-grown tea to some of the UK’s finest hotels, but something didn’t quite add up. And Nicola wasn’t the only person taking an interest in his story. Help support our independent journalism at theguardian.com/sciencepod

The first person has been treated with a highly anticipated new gene therapy that aims to turn back the clock on ageing cells. The trial is aimed at retinal cells, with the hope that encouraging them to behave as if they were young again could improve sight in the affected patients. If it proves to be safe, it could open the door to a whole raft of therapies based on the emerging field of cellular rejuvenation. To understand more about this cutting edge research, Madeleine Finlay hears from science editor Ian Sample and from Paul Knoepfler, professor of cell biology and human anatomy at the university of California, Davis.. Help support our independent journalism at theguardian.com/sciencepod

Scientists often talk about the importance of flora and fauna to the health of our planet, but Dr Toby Kiers, an evolutionary biologist and founder of the Society for the Protection of Underground Networks, wants us to consider another force: fungi. Her work charting the planet’s vital underground systems has earned her numerous awards, including a MacArthur fellowship and a Tyler Prize for Environmental Achievement (sometimes called the ‘green’ Nobel). She tells Ian Sample about her work mapping fungal networks on the remote Palmyra Atoll in the Pacific Ocean, and what the research reveals about fungi’s often invisible role. Help support our independent journalism at theguardian.com/sciencepod

Men’s average testosterone levels have halved over the past 50 years, according to scientists who say society is facing a male fertility crisis. Rising levels of obesity and diabetes are expected to play a part, but the team behind the work suggest that environmental factors such as endocrine-disrupting chemicals – which can be found in various household items – and global heating could also be factors in the apparent striking decline. Ian Sample speaks to science correspondent Hannah Devlin to find out how the work has been received and what the researchers want to see happen in response to their finding. Help support our independent journalism at theguardian.com/sciencepod

In the last 50 years, Britain has lost an astonishing 73 million wild birds from its landscape, according to the British Trust for Ornithology. Habitat loss, pesticides, disease, cats and the climate crisis mean there are fewer birds than ever before. For children and young people it can be difficult to appreciate the scale of the loss due to a psychological phenomenon called ‘shifting baseline syndrome’, where each generation inherits a degraded version of the environment, and therefore doesn’t notice the overall decline. But Gen Z are bucking the trend. Thanks to social media and the Merlin Bird ID app, birding has become cool. To find out what we’re missing from the dawn chorus, and why young people are embracing birdwatching, Madeleine Finlay hears from the writer Robert Macfarlane and from Jess Painter, a member of the RSPB’s youth council. Help support our independent journalism at theguardian.com/sciencepod

Researchers claim they are closer to creating life from nothing after building tiny, quivering blobs that use lab-made DNA to feed, grow and multiply in a dish. To find out how significant this step is, and where scientists hope it will lead, Madeleine Finlay hears from co-host Ian Sample and from Kate Adamala, professor of genetics at the University of Minnesota. Help support our independent journalism at theguardian.com/sciencepod

The Lincoln Memorial reflecting pool in Washington DC has hardly been out of the news since April when President Trump vowed to have it renovated, and painted ‘American flag blue’ by 4 July. Despite the pool being stripped, cleaned, coated and refilled, within days the algae that has plagued it for decades was back. To find out why these blooms happen, what makes them so difficult to tackle and what Trump could try next, Ian Sample hears from co-host Madeleine Finlay, and from Dr Linda May, a freshwater ecologist at the UK Centre for Ecology & Hydrology.. Help support our independent journalism at theguardian.com/sciencepod

How much do our genes determine about our lives, and could they influence traits like risk-taking, antisocial behaviour or even violence? Ian Sample talks to Kathryn Paige Harden, a behavioural geneticist and professor of psychology at the University of Texas at Austin who studies how genetic factors shape human behaviour. In her book Original Sin she explores how nature and nurture combine to influence our likelihood of committing crimes, and asks whether the ‘cause’ of our actions matters for how we think about culpability. Help support our independent journalism at theguardian.com/sciencepod

Met Office forecasters have issued a rare red weather warning for England, with temperatures potentially reaching 40C (104F) in some places. Europe is also dealing with a debilitating heatwave, with schools closed, trains cancelled and France even restricting the consumption of alcohol outdoors to take pressure off the emergency services. The high temperatures coincide with the coming El Niño, which some scientists have nicknamed Godzilla for its predicted strength. To find out whether the two are linked, Ian Sample hears from our Europe climate correspondent, Ajit Niranjan. He explains why it’s so hot, why we could be in for even worse and how we can keep as cool as possible. Help support our independent journalism at theguardian.com/sciencepod

Sea ice is melting fast and worsening the climate crisis. But what if there were a way to thicken it again? Madeleine Finlay is joined by environment editor Damian Carrington to discuss a bold attempt to refreeze the Arctic which is showing early signs of success. He visited the project to find out how it will work, how much it will cost and whether it really has potential to improve the fate of the Arctic’s ice. Help support our independent journalism at theguardian.com/sciencepod

The UK prime minister, Keir Starmer, has announced a social media ban for under-16s, as part of an online safety drive that aims to go even further than the world’s first ban, introduced by Australia last year. Many parents have welcomed the proposals, but scientists have pointed to the lack of strong evidence for the efficacy of bans, and some campaigners have argued that the proposal allows social media companies to avoid making meaningful changes on their platforms. Ian Sample is joined by co-host Madeleine Finlay to explore what the evidence indicates about the harms of social media and the impact of banning it outright. Help support our independent journalism at theguardian.com/sciencepod

A daily pill can double survival time in patients with the world’s deadliest cancer, according to the results of a clinical trial that experts are saying is a gamechanger and one of the biggest breakthroughs in decades. To find out more about how daraxonrasib works and how life-changing it could be for patients, Madeleine Finlay speaks to Prof Naureen Starling, consultant medical oncologist at the Royal Marsden hospital. Help support our independent journalism at theguardian.com/sciencepod

While many dinosaurs were wiped out when a colossal asteroid struck Earth 66m years ago, one group survived: birds. Prof Steve Brusatte, a palaeontologist at the University of Edinburgh, has written a new book, The Story of Birds, tracing the evolution of our feathered friends from their dinosaur origins. He joins science correspondent Nicola Davis to discuss how scales first became feathers, how winged dinosaurs survived the impact of the asteroid and why their extreme adaptability offers hope that birds might also make it through the current environmental crisis. Help support our independent journalism at theguardian.com/sciencepod

It’s just a week until the first whistle of the 2026 World Cup. To mark the occasion, Madeleine Finlay talks to Ian Sample about the science behind the tournament. It’s likely to be one of the hottest ever World Cups, and scientists have written to Fifa asking it to reconsider its heat mitigations for players and referees. Dr Oliver Gibson of Brunel University outlines their concerns. Also on the agenda is the huge fossil-fuel impact of the tournament, and the effect of VAR on the psychology of referees and fans. Help support our independent journalism at theguardian.com/sciencepod

Humans have been wondering why we sleep for thousands of years. Is sleep’s purpose rest and relaxation, memory consolidation or maybe cognitive processing? In the last 15 years, scientists have discovered another possible explanation – waste disposal. In 2012 neuroscientist Maiken Nedergaard’s lab discovered that the brain has its own cleaning process, the glymphatic system, which clears away unhelpful proteins and metabolic byproducts, and only switches on at night. Since that groundbreaking discovery we’ve learned more about what drives this system and, importantly, how it could be impacting dementia. To understand more, Ian Sample talks to Prof Nedergaard about how she made the original discovery and how subsequent work is building a picture of sleep as anything but a quiet and inactive state. Help support our independent journalism at theguardian.com/sciencepod

Last month at Beijing’s half marathon, a robot named Lightning beat the human world record by nearly seven minutes. It’s the latest in a string of AI-powered milestones that have got people wondering whether robots are about to enter our everyday lives, just as chatbots have. And the country leading the charge is China, where the government has pledged to invest more than £100bn in robotics over the next 20 years. To find out how robots are already entering the workforce, and what needs to happen to get them cleaning our homes and weeding our gardens, Ian Sample hears from the Guardian’s senior China correspondent, Amy Hawkins, and from Nathan Lepora, professor of robotics and AI at Bristol University, who researches how robots can achieve human-like dexterity. Help support our independent journalism at theguardian.com/sciencepod

Home red-light therapy devices have exploded in popularity as masks, body wraps and mittens promise to reduce wrinkles, redness and even acne. But do the claims stack up, and what other benefits are scientists investigating? Ian Sample hears from his co-host, Madeleine Finlay, and the consultant dermatologist Dr Jonathan Kentley. Kentley explains how the potential benefits of red light were discovered, how it is thought to interact with collagen in our skin, and what science has to say about its impact on our appearance. Help support our independent journalism at theguardian.com/sciencepod

The US supreme court has preserved nationwide access to mail-order abortion pills – for now. As Carter Sherman explains, the fight to protect this medication is far from over, as a nationwide, near-total abortion ban could be on the horizon. Carter speaks with Dr Angel Foster, co-founder of the Massachusetts Medication Abortion Access Project, who reveals how the legal battle over abortion pills has affected patients across the US – and what could happen next. Help support our independent journalism at theguardian.com/sciencepod

After more than a decade of global consultation, polycystic ovary syndrome – which affects as many as one in eight women – has been renamed. The condition is caused by high levels of androgens, which can lead to symptoms such as excess hair, weight gain and irregular periods. To understand why campaigners wanted it renamed, and what its new name – polyendocrine metabolic ovarian syndrome (PMOS) – could mean for patients, Madeleine Finlay hears from the Guardian’s science correspondent, Nicola Davis, and Rachel, a campaigner from the charity Verity. Help support our independent journalism at theguardian.com/sciencepod

An outbreak of Ebola has emerged in the Democratic Republic of Congo and Uganda, leading to nearly 400 confirmed cases and more than 100 deaths. To find out how the outbreak might have begun, what authorities can do to contain it and why this outbreak is causing particular concern, Ian Sample hears from Daniela Manno, a clinical epidemiologist at the London School of Hygiene and Tropical Medicine. Help support our independent journalism at theguardian.com/sciencepod

The US supreme court dealt a devastating blow to the 1965 Voting Rights Act when it ruled in Louisiana v Callais in April that states cannot consider race in redistricting. Southern states from Tennessee to Alabama have rushed to erase majority-Black districts, sparking chaos for the midterm elections. Kai Wright talks to Stacey Abrams, a voting rights activist and former Georgia house minority leader, about the fallout from the decision, and why, despite it all, she still believes the way forward lies in engaging more voters to participate in democracy. ‘They have fractured communities and said we’re going to scatter these seeds. Our job is to grow,’ she says. Help support our independent journalism at theguardian.com/sciencepod

Madeleine Finlay sits down with co-host and science editor Ian Sample to discuss three eyecatching stories from the week, including an update on hantavirus. Also on the agenda is the Pentagon’s release of a tranche of never before seen documents relating to UFOs, and a study looking at the link between taking part in cultural activities and slower biological ageing. Help support our independent journalism at theguardian.com/sciencepod

Last month President Trump signed an executive order designed to fast track both research and access to psychedelic drugs as treatments for mental health illnesses. The most prominent in the order was ibogaine, a drug derived from the root bark of a West African shrub, that has shown some promise in relieving the long term effects of traumatic brain injury. Madeleine Finlay talks to journalist Mattha Busby about podcaster Joe Rogan’s role in the story, what else is behind the President’s interest in psychedelic research, and what the order will change in practice for scientists and researchers. Help support our independent journalism at theguardian.com/sciencepod

To celebrate Sir David Attenborough’s centenary, Madeleine Finlay catches up with natural history writer Patrick Barkham, who has met the celebrated presenter. They explore how the natural world has changed in the century that Attenborough has been on Earth, and how his programming has reflected his growing commitment to highlighting the devastating impacts of the climate crisis on nature and biodiversity. Help support our independent journalism at theguardian.com/sciencepod

Three people have died after an outbreak of hantavirus onboard a cruise ship travelling from Argentina to Cape Verde. The World Health Organization says a total of seven cases – two confirmed by laboratory testing and five suspected – have been identified on the cruise ship so far. It is also investigating whether rare human-to-human transmission of the virus could be behind the cases. Madeleine Finlay talks to Prof Jonathan Ball from Liverpool School of Tropical Medicine to find out where the virus comes from, how it is transmitted to humans, and what health agencies will be doing to try to contain it. Help support our independent journalism at theguardian.com/sciencepod

The transition towards renewable energy received a boost last week when representatives from 57 countries met in Santa Marta, Colombia, for a world-first climate meeting aimed at bringing the fossil fuels era to an end. Madeleine Finlay hears from the Guardian’s global environment editor, Jon Watts, about how the landmark conference came about, who was missing, and whether the optimism can translate into real world action. Help support our independent journalism at theguardian.com/sciencepod