Clarifying the attribution of recent disaster losses: A response to Epstein and McCarthy

—HANS VON STORCH Institute for Coastal Research, GKSS Research Center, Geesthacht, Germany he December 2004 issue of BAMS contains an article warning of the threats of abrupt climate change (Epstein and McCarthy 2004, hereafter EM04). The article seeks to raise awareness of the risks of an abrupt change in climate related to human influences on the climate system, but, in doing so it repeats a common factual error. Specifically, it identifies the recent growth in economic damages associated with weather and climate events, such as Hurricanes Mitch and Jeanne and tornadoes in the United States, as evidence of trends in extreme events, arguing “the rising costs associated with weather volatility provide another derived indicator of the state of the climate system . . . the economic costs related to more severe and volatile weather deserves mention as an integral indicator of volatility.” Although the attribution of increasing damages to climate changes is but one of many assertions made by EM04, the repetition of this erroneous claim is worth correcting because it is not consistent with current scientific understandings. The rising costs of disasters are important, and so too is human influence on climate. Policy makers should, indeed, pay attention to both issues. But a robust body of research shows very little evidence to support the claim that the rising costs associated with weather and climate events are associated with changes in the frequency or intensity of events themselves.1 Instead, the research that has sought to explain increasing disaster losses has found that the trend has far more to do with the nature of societal vulnerability to those events. This conclusion is borne out in literature from the natural hazards community (e.g., Mileti 1999; Tierney 2001) and the societal impacts of the climate community (e.g., Glantz 2003; Changnon et al. 2000), and is consistent with the findings of the most recent assessment of the Intergovernmental Panel on Climate Change (IPCC) (Houghton et al. 2001; McCarthy et al. 2001).