Clouds formed at sea are key to regulating atmospheric temperatures, and scientists now understand more of the chemistry involved. …vital cogs … utterly invisible and they traffic in potent chemicals on an unbelievable scale.They make the dimethyl sulphide molecules that waft skywards to provide nuclei around which cloud droplets form. When the sun shines brightly they get to work, and the gas they produce then makes aerosols that seed clouds which reflect sunlight and damp down the planetary temperatures again… Marine phytoplankton make a compound called dimethyl-sulfoproprionate or DMSP. They make it on a massive scale: an estimated 10 billion metric tons of the stuff each year…microbial plants flourish to photosynthesise even more of the compound. And then an important group of Pelagibacterales microbes moves in to take the chemical and cleave it, to release two gases. Telltale smells “Everyone knows these gases by their smells”, said Professor Giovannoni. “One of these compounds – dimethyl sulphide or DMS – we recognise as the smell of the sea. The other gas – methanethiol – makes us think of leaking gas lines.