What is El Niño?

The news has been full of references to ‘El Niño’, a global weather phenomenon that, this year, is forecast to be the biggest yet. CrowdScience listener Kennedy is a farmer in Kenya and this has got him worried. He wants to know exactly what El Niño is, why it causes such differing weather patterns all over the world and, most importantly, how it might affect his crops. Always keen to help listeners answer global science questions with local impacts, CrowdScience is on the case. Presenter Anand Jagatia travels to meet oceanographer Ligin Joseph, from the University of Southampton in the UK. Equipped with a tank full of water, a sprinkling of turmeric, some purple dye and a hairdryer, Ligin recreates the Pacific Ocean in his living room. How does changing the hairdryer setting create a mini-El Niño in the tank, and why does that affect the weather everywhere else? Peruvian biologist Rosa Vasquez Espinosa, from Amazon Research International, has already witnessed the effects of El Niño first hand. She tells Anand about the extreme rain and drought Peru has already seen, as well as describing how Peruvian fishermen first observed El Niño hundreds of years ago. And what about CrowdScience listener Kennedy’s crops in Kenya? How can a phenomenon that originates in the South American Pacific have an impact on a country that faces the Indian Ocean, 13,000km away? Hannah Kimani from the Kenya Meteorological Department explains, and has some advice for Kennedy and farmers like him. Presenter: Anand Jagatia Producer: Eloise Stevens Editor: Ben Motley (Photo: Dark clouds with calm dark blue ocean view - stock photo CrowdScience overlay Credit:imagedepotpro via Getty Images)

In November 2016 the BBC World Service launched a brand new show in which listeners would send in their science questions, and a team of fearless presenters would find answers. Ten years on, CrowdScience is still going strong.  We’ve answered over five hundred questions from our listeners, spoken with thousands of scientists and covered subjects from the mundane to the profound. Our audience’s insatiable curiosity has taken us to the bottom of the ocean, to the top of volcanoes and to the edge of a hurricane. We’ve been on adventures in audio that have been surprising, fascinating and breathtaking, all to find answers to questions sent in by CrowdScience listeners. In true CrowdScience fashion, we wanted to celebrate our tenth anniversary with our listeners. We asked the audience for their CrowdScience stories, and to pick some of their favourite moments from the last decade. As a result we’re revisiting some incredible episodes, including butterflies that migrate thousands of kilometres, how to measure the weight of the internet and why cables get tangled. CrowdScience has brought you fascinating stories, intriguing experiments and thought-provoking moments, and we’ll be hearing from listeners who have found our programmes more valuable than we could have imagined. Our tenth anniversary show also gives presenter Anand Jagatia time to chat with other CrowdScience presenters about what makes CrowdScience special, including some unforgettable experiences and moments from the show. With ten years of episodes to choose from, it hasn’t been an easy task.  And with a seemingly inexhaustible supply of questions from curious listeners, we’re already looking forward to the next ten! Presenter: Anand Jagatia Producer: Christine Bennett Editor: Ben Motley

CrowdScience listener Nyok, in South Sudan, is right-handed and has always felt very creative. He's also noticed that left-handed people seem to be more logical. He's wondering if this has anything to do with the idea that different sides of your brain can be dominant for different tasks.We covered the basics on hand preference three years ago, in a CrowdScience episode called ‘Why aren’t we all ambidextrous?’, so presenter Caroline Steel delves into the archive to find out about the evolution of hand preferences. Psychologist Sebastian Ocklenburg from MSH Medical School in Hamburg, Germany, and neuropsychologist Marietta Papadou Pastou from the National and Kapodistrian University of Athens in Greece, explain why most people are right-handed and why we think cultural differences are also a factor.In that show Caroline also spoke to neuropsychologist David Carey from the University of Bangor in Wales. He was so fascinated by Caroline’s answer to a test question that he invited her for a brain scan. Three years later – thanks to Nyok’s question - she’s finally taking him up on the offer!Caroline is mixed handed, which means that she prefers her left hand for some tasks and her right hand for others. So what can an MRI scan tell us about which side of her own brain she’s using? Richard Binny, Director of the Bangor Imaging Institute, slides her into the machine before David talks her through the results.But does which hand you prefer really predict whether you’re more creative, or more logical?Presenter: Caroline Steel Producer: Margaret Sessa-Hawkins with Sam Baker Editor: Ben Motley(Photo: Split Brain Illustration with Mathematical Equations and Neural Networks - stock photo Credit:bymuratdeniz via Getty Images)

CrowdScience listener Lauren from Belgium has near-complete hearing loss in one ear, because all the sensory hair cells in her inner ear have died. This got her thinking about how complicated the human ear is and whether there are other animals with simpler ears, in particular insects. Do they even have ears? Presenter Caroline Steel hears Lauren’s call and sets off on a hunt for insect ears. She discovers that crickets have them just below their knees. In Fernando Montealegre-Zapata’s laboratory at the University of Lincoln in the UK, she serenades a cricket to test just how much of her voice it can hear. But crickets aren’t the only ones with ears. Invertebrate neurobiologist Natasha Mhatre, from Western University in Canada, explains that you can find ears almost anywhere on an insect body – from between the legs of a praying mantis to the mouthparts of a moth. So are there even simpler ears out there? Sensory biologist Joerg Albert from University College London in the UK tells Caroline how male mosquitoes use antennae to listen out for females. But they aren’t exactly simple. In fact, a mosquito probably has more sensory neurons around their antennae than you are using to hear right now. And what about the insects that can’t hear? Scientist Jayne Yack from Carleton University in Canada unveils the hidden world of vibroscapes. Caterpillars on a leaf, for example, can sense the vibrations created by peers, predators, and even airborne sounds. Which makes Caroline wonder: when does vibration sensing actually become hearing? Presenter: Caroline Steel Producer: Florian Bohr Editor: Ben Motley(Photo: Insect singing and playing the guitar in flamenco concert - stock photo Credit: Fernando Trabanco Fotografía via Getty Images)

Some animals lay eggs, and their young hatch out of them. Other animals give birth to live young. But which strategy is best? That’s the question that’s been bothering CrowdScience listener Sameer in Canada. Is giving birth to live young a good reproductive strategy? It takes a lot of time and effort, and it doesn’t result in that many offspring. Egg-laying, on the other hand, allows you to produce lots of young at one time to maximise the chance of survival, seems easier than giving birth, and you can lay eggs more often. So why have humans and most other mammals evolved to give birth to live young? To find the answer, presenter Anand Jagatia travels way back into the past with Paul Barrat from London’s Natural History Museum in the UK to look at the evolutionary history and advantages of egg-laying. What have gravity and moisture got to do with the success of an egg? Palaeontologist Kimi Chapelle from Stony Brook University in the US shows Anand the oldest eggs ever found, and we discover why even older eggs are missing from the fossil record. We discover how the evolution from egg-laying to birth-giving is happening right in front of our eyes, with Camilla Whittington from the University of Sydney, Australia. And we might even have an answer to the age-old question about eggs - which came first? You can see the oldest eggs ever found here: https://www.nhm.ac.uk/discover/news/2020/april/most-detailed-look-inside-worlds-oldest-dinosaur-eggs.html(Photo: A chick hatching from egg on egg tray. Credit: David Malan/Getty Images)Presenter: Anand Jagatia Producer: Margaret Sessa-Hawkins Editor: Ben Motley

Have you ever found yourself doing something – perhaps getting a glass of water, eating a snack, or even sitting on the toilet – without remembering making the decision to do it? CrowdScience listener Mohammed certainly has. It’s left him wondering: does he really have free will, or is he a puppet of his biological processes? To try and find the answer, we start in the brain. Presenter Caroline Steel meets neuroscientist Uri Maoz, from Chapman University in the US, to explore the controversial research into what happens when we make decisions. Does neuroscience say that we are free to make our own choices, or does our brain make decisions outside of our consciousness? Then there’s our guts - they’re home to trillions of microbes; independent living creatures that we couldn’t live without. But could these tiny organisms influence more than our digestion? Harriët Schellekens, from University College Cork in Ireland, shares her cutting-edge research into the surprising ways our microbes shape us. And perhaps some of us are more "in charge" than others. Caroline visits Sarah Garfinkel at University College London in the UK, to have her interoception tested - her ability to sense what’s happening inside her body. How closely is she tuned into what's going on inside her gut, and why might that matter? Meanwhile, at King’s College London, health psychologist Lauren Heathcote is exploring how this internal sense could be used in therapy. Caroline meets cancer patient Nadia Haynes to discover how learning to listen to her body has actually changed her sense of control. Presenter: Caroline Steel Producer: Katie Tomsett Editor Ben Motley(Photo: Close-up Of Businessman's Hands - stock photo Credit: AndreyPopov via Getty Images)

Where do shells come from? CrowdScience listener Tamsyn got in touch, a little embarrassed, confessing that she had managed to reach her twenties without realising that shells are made by living creatures. Suddenly, her curiosity ran wild and she asked CrowdScience to investigate how these sea creatures have the architectural prowess to make shells in delicate ornamental shapes with beautiful colours and patterns. The job of sea-creature-investigator-in-chief falls to presenter Marnie Chesterton. She heads to the Natural History Museum in London, UK, where they have more shells than they can keep count of. Researcher Dr Suzanne Williams pulls out drawer after drawer of amazingly varied molluscs for Marnie to marvel at. Then, it’s off to the beach to go shell hunting with Dr Leanne Melbourne, Senior Curator of Climate Change and the Dynamic Coast for Norfolk Museums in the UK. They look at the structure of shells, and Leanne explains how a soft mollusc is able to make a hard shell so sturdy they can survive for millions of years. Marnie then gets into some mollusc maths. With shells strewn across a table, Professors Alain Goriely and Derek Moulton at the University of Oxford, UK show Marnie how they have mapped their shapes. Can Marnie uncover the formula that underpins the formation of shells, from the most basic to the inexplicably ornate? Presenter: Marnie Chesterton Producer: Tom Bonnett Editor: Ben Motley(Photo: Close up of young womans hands holding seashells, Eilat, Israel - stock photo Credit: PhotoStock-Israel via Getty Images)

CrowdScience listener Gurmeet in India wants to know if plants can sense that we're around. She started wondering about this at a wellness centre where she was encouraged to hug a tree. She enjoyed the experience, but what about the tree? Did it enjoy being touched? And is there actually evidence that hugging a tree is good for us? Anand Jagatia talks to scientists about what happens to a plant when it's touched. Molecular biologist Olivier van Aken, from Lund University in Sweden, explains what happens inside a plant's cells – from mimosa whose leaves close up when touched to a Venus flytrap that sees a good opportunity for dinner. Plant biologist Alexander Jones, from the Sainsbury Laboratory at the University of Cambridge, UK, tells Anand how plants process information without a brain: when there's a threat from a hungry insect, it's their hormones that leap into action to defend it. Anand visits Wisley Garden in the UK and meets Ashby Lavelle Sachs, the Royal Horticultural Society's Wellbeing Fellow, who explains why being in nature is so good for our physical and psychological health. And he talks to South Korean researcher Sinae Park, from Konkuk University in Seoul, about the impact of touching plants with different types of foliage – in an experiment, she found that it's the soft and smooth plants that made participants feel most relaxed. It turns out that plants find the whole experience of being touched pretty stressful. So next time you hug a tree, you might be getting a whole lot more pleasure out of it than the tree does. Presenter Anand Jagatia Producer Jo Glanville Editor Ben Motley(Photo- I love you nature! Nature and people - stock photo Credit: Kieferpix via Getty Images)

CrowdScience listener Devin in Canada has just had a baby. Worried that all the good email addresses might be taken by the time his child needs one, he has already set up an account. But it got him wondering: how many email addresses belong to people who have died? From websites and blogs to email accounts, social media profiles, gaming avatars and even our conversations with AI, we’re all leaving behind a trail of digital footprints that can outlive us. So what happens to them when we die? Are they deleted, recycled or preserved? And who gets to decide? Presenter Anand Jagatia travels beyond the digital veil and into the internet’s afterlife to find out. Professor Edina Harbinja from the University of Birmingham Law School in the UK, an expert in ‘digital death’ and ‘post-mortem privacy’, explains how the law has struggled to keep pace with our digital lives. While it’s relatively straightforward to decide who inherits physical letters and photographs, what happens when those memories are stored in emails or on social media? For artist Janilda Bartolemeu, encountering messages from her father on Facebook long after his death was like interacting with a ghost. Anand visits her artwork at IMPAKT gallery in Utrecht, Netherlands, part of the exhibition Data Never Dies, where curator Rosa Webers explores how art can help us understand the human impact of technology. Finally, sociologist Professor Carl Öhman of Uppsala University in Sweden reveals that the number of dead people online will outnumber the living sooner than we might think. It raises profound questions about how we understand the internet, and ourselves within it. Presenter: Anand Jagatia Producer: Emily Knight Editor: Ben Motley(Photo: Grave on laptop computer, 3d render - stock photo Credit: Brankospejs via Getty Images)

CrowdScience listener Lisa, who is from South Africa but now lives in the UK, has been a vegetarian for many years. Sometimes though, she still finds herself craving meats – like spaghetti bolognese or a burger. To satisfy these cravings, she eats ‘alt-meats’, products meant to look and taste like meat but made from vegetables. This has her wondering though, are these alternative meats better for the planet than actual meat would be? And what about her health? Given that many of these foods are highly processed, would eating meat be better for her? Presenter Chhavi Sachdev speaks to food systems researcher Charlotte Bunge from Uppsala University on Sweden, US health journalist Alice Callahan and researcher Christopher Gardner from Stanford University in the US to try and pick apart the positives and negatives of replacing ‘real’ meat with ‘pretend’ meat, before visiting an Indian company producing meat that was grown in a lab. Presenter: Chhavi Sachdev Producer: Margaret Sessa-Hawkins Editor: Ben Motley(Photo:Raw frankfurter sausage on a fork isolated - stock photo Credit:Andrey Sayfutdinov via Getty Images)