ABSTRACT
Talk of tipping points is now commonplace in climate science and policy and also in the media. Concerns that the prevailing linear models of climate change could be wrong were fi rst voiced in the late 1980s. Scientists started to warn that environmental changes would not be smooth, gradual events but sudden “sharp jumps” (Broeker 1987: 123). Since then, warnings of abrupt, nonlinear climate change effects have been commonplace rhetoric for environmental campaigners and scientists alike (for example, Mastrandrea and Schneider 2001; Alley et al. 2005). Abrupt, nonlinear climate change effects are considered more pernicious, because they will shock human and environmental systems that will in turn struggle to adjust. As the concept of abrupt climate change effects became accepted, it was linked to the concept of tipping points, which had its origins in describing social change (for instance, Gladwell 1996). Tipping-point rhetoric has three elements, all captured by Hansen’s much-quoted statement, at the beginning of this chapter. The fi rst is irreversibility: once a tipping point is passed there is no return. The second is the abruptness of the change.
