Drastic temperature drop on an Earth-like terra-planet

The video below shows the development of surface temperature and precipitation of a land-only planet during the transition from its hot and dry to its cold and wet state. The simulations have been performed with ICON-ESM, setting atmospheric composition and orbit conditions as for present day Earth, except for obliquity being zero.

The terrestrial hydrology of this planet is made special by assuming a globally constant ground water level. Thereby the atmospheric access to surface water is limited, in contrast to an aqua planet. This limited access to water causes bi-stability in this system: At high surface albedo only the wet and cold state exists, which resembles present day climate, where water evaporated in the tropics is also largely precipitated in the tropics. At low surface albedo a second state exists, the hot and dry state, being 20K warmer. Here the tropics are completely dry because all water evaporating there is exported to the extra-tropics.

In the simulation, the model is started in the hot and dry state, using a value for surface albedo such that it is unstable. In the transition to the cold and wet state first mean global temperature decreases only slightly. Then, after the emergence of precipitation at the equator, the temperature drop accelerates until finally the equatorial and extra-tropical precipitation bands converge.