Paying extra to offset your carbon emissions may sound like a good idea. But does planting trees or paying to save a rainforest actually reduce your carbon footprint? Travel writer Manchán Magan and climate scientist Thales West explain why they're sceptical. We also hear from one of America's leading airlines, United, which is increasing the number of flights powered by waste products and old cooking fat. United's head of global environmental affairs Lauren Riley tells us more.

Photo: A plane casts a shadow over a forest (Credit: Getty)