The amount of CO₂ in the atmosphere is controlled by a balance between addition by outgassing from Earth's interior and removal by chemical reactions between water and silicate rocks ('silicate weathering') that remove CO₂ from the air and lock it in carbonate rocks on the seafloor. Silicate weathering goes faster when the Earth is warmer and slower when cold so CO₂ decreases when Earth warms and accumulates it cools, opposing climate swings. This keeps Earth's climate within a habitable range for life. But it is unknown whether silicate weathering goes faster because hotter temperatures accelerate the chemical reactions or if it is because warming leads to more rainfall, bringing more water into contact with the silicate rocks and carrying more weathering products to the sea.

Using computer models of climate and silicate weathering, we find that those two scenarios (temperature control; water control) produce different relationships between climate and continental geometry. Comparing with Earth's reconstructed temperature and continents over the past 480 million years (Myr), we find evidence that most time was spent under temperature control, except a period with water control from approximately 300 to 200 Myr ago, coinciding with the supercontinent Pangea's existence, when Earth was unusually arid.