New research shows that penguin guano in Antarctica is an important source of ammonia aerosol particles that help drive the formation and persistence of low clouds, which cool the climate by reflecting some incoming sunlight back to space.

The findings reinforce the growing awareness that Earth’s intricate web of life plays a significant role in shaping the planetary climate. Even at the small levels measured, the ammonia particles from the guano interact with sulfur-based aerosols from ocean algae to start a chemical chain reaction that forms billions of tiny particles that serve as nuclei for water vapor droplets.