Dust has the potential to modify global climate by influencing the radiative balance of the atmosphere and by supplying iron and other essential limiting micronutrients to the ocean. Indeed, dust supply to the Southern Ocean increases during ice ages, and ‘iron fertilization’ of the subantarctic zone may have contributed up to 40 parts per million by volume (p.p.m.v.) of the decrease (80–100 p.p.m.v.) in atmospheric carbon dioxide observed during late Pleistocene glacial cycles.