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Abrupt Climate Change: Inevitable Surprises
PLATE 6 Paths along the solution curves of two versions of Stommel’s box model showing the rate of the ocean overturning when the freshwater forcing flux H is increased and then decreased. Only in the case of weak diffusion (orange) does the model respond with an abrupt change, once a threshold in H is crossed. In the case of strong diffusion (green), at any time, there is a unique equilibrium.
PLATE 7 Changes in Atlantic circulation in different models forced by prescribed increases in atmospheric CO2. Most models show a reduction of the THC in response to increasing greenhouse gas forcing (Intergovernmental Panel on Climate Change, 2001b).