Svante August Arrhenius proposed in 1884 (Investigations on the galvanic conductivity of electrolytes) that, when dissolved in water, electrolytes dissociate into electrically opposite positive and negative ions. In 1896 he discovered that the amount of carbon dioxide in the atmosphere determines the global temperature and theorized that ice ages were linked to reduced carbon dioxide levels. Arrhenius won the Nobel Prize in chemistry in 1903.