¹ That cosmic impacts (whether from asteroids or comets) of modest magnitude can cause very destructive tsunamis is shown in Ward and Asphaug (2000) and Chesley and Ward (2006); see also the Chapter 11 in this volume.

² Deaths caused by Hurricane Katrina were a small fraction of overall loss relative to property damage, lost earnings, and other readily monetizable costs. The ratio was reversed in the case of the Indian Ocean tsunami, where 300,000 people were killed versus only 1200 from Katrina.

³ Of course, notall Americans are ‘prime-aged workers’, butitis notclear thatothers have lower values of life. Economists compute value of life by dividing how much a person is willing to pay to avoid a risk of death (or insists on being paid to take the risk) by the risk itself. Elderly people, for example, are not noted for being risk takers, despite the shortened span of life that remains to them; they would probably demand as high a price to bear a risk of death as a prime-aged worker -indeed, possibly more.

⁴ The ‘wait and see’ approach is discussed further below, in the context of responses to global warming.

⁵ This calculation is explained in Posner (2004, pp. 167–70).

⁶ There is evidence thatglobal warming is responsible in partatleastfor the increasing intensity of hurricanes (Emanuel, 2005; Trenberth, 2005).

⁷ For an optimistic discussion of the scientific and economic feasibility of trapping carbon dioxide before it can be released into the atmosphere and capturing it after it has been released, see Socolow (2005).

⁸ In fact, scientists have already reported dramatic effects from global warming in melting Arctic glaciers and sea ice (Hassol, 2004).

⁹ The length of the ‘short run’ is, unfortunately, difficult to specify. It depends, in the present instance, on how long it would take for producers and consumers of energy to minimize the impact of the price increase by changes in production (increasing output in response to the higher price) and consumption (reducing consumption in response to the higher price).

¹⁰ For further readings in the subject matter of this chapter, see Patricia Grossi and Howard Kunreuther, eds., Catastrophe Modeling: A New Approach to Managing Risk (Springer, 2005); Michael J.S. Belton et al., eds., Mitigation of Hazardous Comets and Asteroids (Cambridge University Press, 2004); Raymond S. Nickerson, Cognition and Chance: The Psychology of Probabilistic Reasoning (Lawrence Erlbaum Associates, 2004); OECD, Large-scale Disasters: Lessons Learned (Organisation for Economic Co-operation and Development, 2004); Richard A. Posner, Catastrophe: Risk and Response (Oxford University Press, 2004); Keith Smith, Environmental Hazards: Assessing Risk and Reducing Disaster, 4th ed. (Routledge, 2004); Martin Rees, Our Final Hour: A Scientist’s Warning: How Terror, Error, and Environmental Disaster Threaten Humankind’s Future in this Century – On Earth and Beyond (Basic Books, 2003).