Drastic drop in temperature 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 were 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 characterized by the hypothesis of a globally constant groundwater level. Thereby the atmospheric access to surface water is limited, in contrast to an aqua planet, which only consists of water. This limited access to water causes bistability in this system, i.e. two stable states of equilibrium: 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 20 K warmer. Here the tropics are completely dry because all water evaporating there is exported to the extratropics.

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