Impact of Continental Configuration on the Climate Response to Greenhouse‐Gas Forcing in an Idealized GCM

Abstract The influence of continental configuration on the climate response to greenhouse‐gas forcing remains poorly understood. Here, we use an idealized model with varying land‐ocean coverage to investigate how the spatial distribution of land modulates the climate response to increased carbon‐dioxide concentrations. When land is concentrated in tropical regions, equilibrium climate sensitivity is lower due to a weaker water‐vapor feedback, land‐ocean warming contrasts are minimal, and global‐mean land relative humidity declines only slightly. By contrast, when land is concentrated in polar regions, equilibrium climate sensitivity is higher, land‐ocean warming contrasts are pronounced, and global‐mean land relative humidity declines substantially. Large land‐ocean warming contrasts also occur when land is arranged in a continuous pole‐to‐pole meridional band. Changes in near‐surface land relative humidity can be attributed to changes in land evaporation and oceanic moisture transport. Together, these results highlight the critical role of continental configuration in shaping Earth's climate response to greenhouse‐gas forcing.