Manabe and Stouffer (1993) pioneered the demonstration of a transition under future warming; an improved model showed a shutdown was especially likely with rapid increase of greenhouse gas emissions, Stocker and Schnitter (1997); see also Broecker (1997); Wood et al. (1999); summary: Rahmstorf (1999); Ganopolski and Rahmstorf (2001) for
instability during a glacial period; IPCC (2001a), pp. 439 - 40.