Climate Change and Human Health Impacts in the United States: An Update on the Results of the U.S. National Assessment

Ebi, Kristie L.; Mills, David M.; Smith, Joel B.; Grambsch, Anne

Several recent studies (e.g., Davis et al. 2002 Davis et al. , 2003a Davis et al. , 2003b ) examined U.S. trends in mortality attributable to elevated temperatures at several locations. Collectively, these studies argue that there has been a declining trend in heat-attributable mortality in U.S. cities from the 1960s through the 1990s, although important regional differences remain (e.g., elevated mortality in northeastern and northern interior cities). An interpretation of these results is that estimates of future temperatureattributable mortality that fail to account for this trend, and instead use some central tendency estimate, will overestimate the mortality impact of future heat events. These studies can be viewed as an argument that there is an adaptive trend in the United States that will minimize the future health impacts of extreme heat events and that climate change will have little impact in shaping future mortality in U.S. cities (Davis et al. 2004 ). Sheridan and Dolney (2003) reported results contradicting the HSA's conclusion that residing in urban areas elevated one's health risks during heat events, partly as a result of the urban heat island effect. Sheridan and Dolney (2003) failed to find a statistically significant difference in the percentage increase in daily mortality and the level of urbanization using data from Ohio for 1975-1998. Although not conclusive as a single result, the study identifies a relevant area for future research on shaping adaptive responses by drawing attention to the risks faced by rural populations during heat events.