What are the clouds like where you are? When you look upwards can you see great tufts of cotton wool, or do they stretch off into the distance, flat like sheets. Are they dark greys and purples, bringing the promise of rain or maybe there aren’t any at all. For listener John from Lincolnshire in the UK clouds looking up at the clouds is a favourite pastime and he wants to know why they look the way they do and why they are so different from one day to the next. Join Presenter Marnie Chesterton as we turn our gaze skyward to discover what gives clouds their shape. Join us for a cloud spotting mission with Gavin Pretor-Pinney, founder of the cloud appreciation society as he helps us de-code the shapes across the sky to reveal what they can tell us about our atmosphere. Dr Claire Vincent at the University of Melbourne introduces us to one of the superstars of the cloud world, Hector the Convector to explain where thunderstorms come from. And we learn how people like you can help NASA to understand the clouds better with Marilé Colón Robles project scientist at the GLOBE programme. Presented by Marnie Chesterton and Produced by Emily Bird [Image: Dramatic looking clouds. Credit: Getty Images]

As someone who dislikes crowds, listener Graham is curious about them. Crowds gather in all sorts of places, from train stations and football matches, to religious events and protest marches. But is there a science behind how they move and behave? To find out, Anand Jagatia speaks to some actual crowd scientists. He learns about the psychology of social identity, which influences everything from how close we stand to others to how we react in emergencies. He visits the Athens marathon, and hears about the algorithm that predicts how 50,000 runners will move through a city on race day. And he explores research into the science of riots, which explains why some peaceful crowds turn violent. Presented and produced by Anand Jagatia Contributors: Dr Anne Templeton, University of Edinburgh Marcel Altenburg, Manchester Metropolitan University Prof John Drury, University of Sussex Archive: BBC News Image: Crowd from above. Creidt: Getty Images

Why don’t we fall out of bed when we’re asleep? That’s the question that’s been keeping CrowdScience listener Isaac in Ghana awake, so presenter Alex Lathbridge snuggles up with some experts to find the answer. We get a lot of emails about sleep, so we’ve gathered together some of our favourite questions and put them to academics working on the science of snoozing. We’re wondering why some people laugh in their sleep, why some people remember their dreams and not others, and why we need to sleep at all - can’t we just rest? Our slumber scholars tell us about how our bodies continue to gather information while we’re asleep, how the tired brain is more likely to remember negative experiences, how we mimic other people in our sleep, and how sleep makes you more attractive to other people. And Alex takes a trip to the zzzzoo to meet some animals that have very different sleep patterns to humans. It’s his dream assignment. Contributors: Vanessa Hill, University of Central Queensland Professor Russell Foster, University of Oxford Mark Kenward, Drusillas Zoo Park Presented by Alex Lathbridge Produced by Ben Motley for the BBC World Service [Image: Man Falling into bed. Credit: Getty Images]

After learning how long it will take the Earth's ice sheets to melt in the previous episode, we continue our journey in Greenland. As world leaders gather in Egypt for the annual UN climate conference, listener Johan isn't too optimistic about governments' ability to curb greenhouse gas emissions and get a handle on climate change. So from his coastal perch in Denmark, he has asked where we should live when the poles have melted away and coastlines creep inland. Along with the help of BBC correspondents around the world, Marnie Chesterton scours the globe for the best option for listener Johan's new home. BBC Mundo reporter Rafael Rojas takes us to a manmade island off Colombia's Caribbean coast to see how we might be able to live with the seas. Meanwhile, reporter Furkan Khan takes us into the high, cold desert region of Ladakh to see if heading for the hills might be the answer. As Marnie searches for a climate-proof destination, she speaks to conservation biogeographer Matt Fitzpatrick, from the Appalachian Laboratory at the University of Maryland Center for Environmental Science. He's made a map that shows what towns and cities will feel like in 60 years and where you should visit in order to get a preview of your home's future climate. But Matt also tells us that we might not be the only ones on the move. And as climate scientist Ruth Mottram from the Danish Meteorological Institute tells us, waters are not going to rise evenly around the world. So can Marnie find a place to go, away from the expanding seas? Additional contributors: Alexander Atencio, environmental sustainability teacher, Santa Cruz del Islote, Colombia Sebastian Martinez, local leader, Santa Cruz del Islote, Colombia Professor Mohammad Din, Ladakh Environment and Health Organisation Ellen and Carl Fiederickson, teacher and sheep farmers, Qassiarsuk, Greenland Presenter: Marnie Chesterton Producer: Sam Baker

We know the Earth's atmosphere is warming and it's thanks to us and our taste for fossil fuels. But how quickly is this melting the ice sheets, ice caps, and glaciers that remain on our planet? That's what listener David wants to know. With the help of a team of climate scientists in Greenland, Marnie Chesterton goes to find the answer, in an icy landscape that's ground zero in the story of thawing. She discovers how Greenland’s ice sheet is sliding faster off land, and sees that the tiniest of creatures are darkening the ice surface and accelerating its melt. CrowdScience explores what we're in store for when it comes to melting ice. In the lead-up to yet another UN climate conference, we unpack what is contributing to sea level rise – from ice sheets in Greenland and Antarctica, to melting mountain glaciers and warming oceans. There's a lot of ice at the poles. The question is: how much of it will still be there in the future? Research Professor and climate scientist Jason Box from the Geological Survey of Denmark and Greenland shows us how much ice Greenland we've already committed ourselves to losing, even if we stopped burning all fossil fuels today. His team, including Jakob Jakobsen, show us how these scientists collect all this data that helps feed climate models and helps us all to understand how quickly the seas might rise. Professor Martyn Trantor from Aarhus University helps us understand why a darkening Greenland ice sheet would only add to the problem of melting. And climate scientist Ruth Mottram from the Danish Meteorological Institute breaks down how the ice is breaking down in Antarctica and other glaciers around the world. Presented by Marnie Chesterton and produced by Sam Baker for the BBC World Service Image: Greenland ice sheets. Credit: Getty Images