Hurricanes and Global Warming

issues of science and politics. Because of their significant and visceral impacts, discussion of extreme events is a frequent locus of such conflation. Linda Mearns, of the National Center for Atmospheric Research (NCAR), aptly characterizes this context: “There’s a push on climatologists to say something about extremes, because they are so important. But that can be very dangerous if we really don’t know the answer” (Henson 2005). In this article we focus on a particular type of extreme event—the tropical cyclone—in the context of global warming (tropical cyclones are better known in the United States as hurricanes, i.e., tropical cyclones that form in the waters of the Atlantic and eastern Pacific oceans with maximum 1-min-averaged surface winds that exceed 32 m s–1). In our discussion we follow distinctions between event risk and outcome risk presented by Sarewitz et al. (2003). “Event risk” refers to the occurrence of a particular phenomenon, and in the context of hurricanes we focus on trends and projections of storm frequencies and intensities. “Vulnerability” refers to “the inherent characteristics of a system that create the potential for harm,” but are independent from event risk. In the context of the economic impacts of tropical cyclones vulnerability has been characterized in terms of trends in population and wealth that set the stage for storms to cause damage. “Outcome risk” integrates considerations of vulnerability with event risk to characterize an event that causes losses. An example of outcome risk is the occurrence of a $100 billion hurricane in the United States. To calculate such a probability requires consideration of both vulnerability and event risk. This article discusses hurricanes and global warming from both of these perspectives.