Blame today's clouds on last month's sun

When microscopic plankton in the shallow sea encounter sunlit skies, the upshot is a cloud-forming compound called dimethyl sulfide (DMS). Although researchers had long suspected a link between DMS production, ocean biota, sunlight, and cloud formation, the exact connection was unknown. Oceanographers in Spain have now figured out that the relationship is a negative feedback loop (Science 2007, 315, 506). DMS is the largest natural source of atmospheric sulfur and a precursor to cloud-forming aerosols. By using oceanographic data from around the world, Sergio M. Vallina and Rafel Sim?? at the Institute for Ocean Sciences, Barcelona, found that during sunny periods, ocean biota release more DMS, which in turn brings about cloud formation and a consequent reduction of DMS production.