• natural hazards;
  • mitigation;
  • warning;
  • forecasting

Natural hazards research seeks to help society develop strategies that appropriately balance risks and mitigation costs in addressing potential imminent threats and possible longer-term hazards. However, because scientists have only limited knowledge of the future, they must also communicate the uncertainties in what they know about the hazards. How to do so has been the subject of extensive recent discussion [Sarewitz et al., 2000; Oreskes, 2000; Pilkey and Pilkey-Jarvis, 2006]. One approach is General Colin Powell's charge to intelligence officers [Powell, 2012]: “Tell me what you know. Tell me what you don't know. Then tell me what you think. Always distinguish which is which.” In dealing with natural hazards, the last point can be modified to “which is which and why.” To illustrate this approach, it is helpful to consider some successful and unsuccessful examples [Stein, 2010; Stein et al., 2012].