  Over its multibillion-year history, the Earth has experienced a wide range of
climates. The long-term climate is controlled by the atmospheric carbon dioxide
concentration, which is regulated by marine sequestration through chemical
weathering. This chemical weathering sink is strongly linked to the
distribution and composition of the continents. However, the effect of
continental distribution has never been studied within a general framework.
Here we show that the global weathering rate is sensitive to the size and shape
of the continents, but is not well explained by the amount of land in the
tropics. We construct synthetic continental configurations and use an ensemble
of global climate model simulations to isolate the expected effect of
continental arrangement on weathering and carbon burial. Runoff patterns are
complex, sensitive to detailed features of continental geometry, and poorly
predicted by continental latitude. These results help explain the long-term
variability and irregularity of Earth's climate.
