The paper by Manabe and Stouffer investigates two stable equilibria in a coupled ocean-atmosphere model, which were discovered during studies on climate sensitivity to CO2 forcing. The model consists of general circulation models for the atmosphere and the world oceans, along with a simple model for land surfaces. Starting from different initial conditions under identical boundary conditions, the model exhibits two stable equilibria: one with a vigorous thermohaline circulation in the North Atlantic and relatively saline, warm surface water, and another without thermohaline circulation and an intense halocline in the surface layer at high latitudes. The air-sea exchange of water is adjusted to remove a systematic bias that suppresses the thermohaline circulation in the North Atlantic. These results suggest that the coupled system may have at least two equilibria and that the thermohaline overturning in the North Atlantic is crucial for maintaining higher surface salinity in the northern North Atlantic compared to the northern North Pacific. The study also discusses the paleoclimatic implications of these findings for the large and abrupt transitions between the Allerød and Younger Dryas events about 11,000 years ago.The paper by Manabe and Stouffer investigates two stable equilibria in a coupled ocean-atmosphere model, which were discovered during studies on climate sensitivity to CO2 forcing. The model consists of general circulation models for the atmosphere and the world oceans, along with a simple model for land surfaces. Starting from different initial conditions under identical boundary conditions, the model exhibits two stable equilibria: one with a vigorous thermohaline circulation in the North Atlantic and relatively saline, warm surface water, and another without thermohaline circulation and an intense halocline in the surface layer at high latitudes. The air-sea exchange of water is adjusted to remove a systematic bias that suppresses the thermohaline circulation in the North Atlantic. These results suggest that the coupled system may have at least two equilibria and that the thermohaline overturning in the North Atlantic is crucial for maintaining higher surface salinity in the northern North Atlantic compared to the northern North Pacific. The study also discusses the paleoclimatic implications of these findings for the large and abrupt transitions between the Allerød and Younger Dryas events about 11,000 years ago.