Informed consent Facebook has been under fire for running a controversial 'emotion manipulation' study on 689,003 Facebook users. The experiment, to find out whether emotions were contagious on the social network, involved minor changes to users' news feeds. It's contentious because the users were not informed that they were taking part in an experiment. Facebook says, check the terms and conditions, but Dr Chris Chambers at Cardiff University says that the ethical standards for science are higher, and should involve informed consent. Dan O'Connor, Head of Medical Humanities at the Wellcome Trust, gives a short history of consent in experimentation.

El Nino According to the Met Office, the world is almost certain to be struck by the "El Nino" phenomenon this year, with the potential to induce "major climactic impacts" around the world. Roland Pease investigates this flip in the climate state of the Pacific basin, and asks the experts studying this phenomenon, whether it'll be a major event and how it might affect the climate.

Gravitational Waves The announcement, earlier this year, that the BICEP 2 telescope at the South Pole had detected evidence that gravitational waves exist may have been premature. Gravitational waves are theoretical phenomena, based on observation of polarisation of ancient cosmic light. Finding them, adds to the evidence that the Universe is expanding. The data has now been made public, but the confidence in the numbers is being questioned.

Cloud cover A listener asks about cloud cover and night time temperatures, and how air temperature and moisture content interact. Our expert Peter Sloss from the Met Office answers.

Producer: Fiona Roberts.