There is a remarkable and recurring shape in both art and science. Hogarth, the seventeenth-century artist, would have seen it as an “S”-shaped “line of beauty,” and Verhulst, the mathematician, in 1838, as yet another example of rapid but self-limiting growth in the form of the logistic equation. And for me it is a powerful model of how social, behavioral, and technological change takes place. So whether we are charting the proportion of the public expressing concern for global warming over time or the number of people, institutions, and countries taking action to limit climate change, we hope the eventual path will be “S”-shaped. Such a curve would show a slow increase of climate change risk perceptions, mitigation or adaptation policies, and individual behaviors followed by a period of rapid growth, until finally the rate of growth slowed once a very large proportion (but not all) of people, institutions, or countries have changed.

The chapters in this volume suggest that if we were to plot public awareness of global warming or climate change we are probably high on the curve, although much of public knowledge of causes and solutions may be inaccurate by scientific standards. Yet public concern and political will have not yet turned the corner leading to an adequate response to this threat. And indeed if we use as a criterion specific actions, rather than vague ones such as “saving energy” or “helping the environment” – then it is still very early days.