Victoria Gill talks to climate scientist Friedericke Otto about the Intergovernmental Panel on Climate Change's new landmark report. The report this week states that the evidence for humanity's role in changing global change is now unequivocal. Dr Otto was a lead author on the chapter on extreme weather events and explains how human influence can be attributed to the increasing incidence and intensity of heat waves and heavy rainfall events. Also in the programme: Immunological evidence to support a covid vaccine booster programme in the UK, with virologist Jonathan Ball of the University of Nottingham. Faecal transplants that rejuvenated the memory and the brains of elderly mice, with neuroscientist John Cryan of University College Cork. A website for the public to report their sightings and upload their videos of ball lightning, with electrical engineer Karl Stephan of Texas State University, San Marcos.