Clouds are one of the biggest challenges for predicting the future climate – on the one hand, they block sunlight from coming in; on the other hand, they trap heat at the surface. It’s especially hard to model clouds over the Southern Ocean, which reflect much more sunlight than our models predict. The surprising cause is the ocean’s marine life, stinking up the Earth’s cleanest air. Dr Marc Mallet will explain this link between the ocean and atmosphere, what this means for the climate system, and whether there are any silver linings in the future.