Quantifying the health impacts of future changes in temperature in California Bart Ostro a,b,n , Stephen Rauch a , Shelley Green a a Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA b Centre for Research in Environmental Epidemiology, Barcelona, Spain article info Article history: Received 18 March 2011 Received in revised form 17 August 2011 Accepted 24 August 2011 Available online 4 October 2011 Keywords: Temperature Heat waves Mortality Morbidity Health Impacts abstract Background: Several epidemiological studies demonstrate associations between high summer tem- peratures and increased mortality. However, the quantitative implications of projected future increases in temperature have not been well characterized. Objective: This study quantifies the effects of projected future temperatures on both mortality and morbidity in California, including the potential effects of mitigation. Data and methods: We first estimated the association between temperature and mortality for populations close to weather stations throughout the state. These dose–response estimates for mortality were then combined with local measures of current and projected changes in population, and projected changes in temperature, using a baseline of average temperatures from 1961 to 1990, for the years 2025 and 2050. The latter were based on two greenhouse gas emissions scenarios (A2 and B1) developed for the Intergovernmental Panel on Climate Change. In addition, we assessed the impacts of future adaptation through use of air conditioners. Several sensitivity analyses were conducted to determine the likely range of estimates. Results: These analyses indicate that for the high emissions scenario, the central estimate of annual premature mortality ranges from 2100 to 4300 for the year 2025 and from 6700 to 11,300 for 2050. The highest estimates are from the models that use age-specific dose–response functions, while the low estimates are from the models that adjust for ozone. Estimates using the low emissions scenario are roughly half of these estimates. Mitigation based on our estimates of the effects of 10% and 20% increase in air conditioner use would generate reductions of 16% and 33% in the years 2025 and 2050, respectively. Conclusion: Our estimates suggest significant public health impacts associated with future projected increases in temperature. & 2011 Elsevier Inc. All rights reserved. 1. Introduction Studies from cities around the world have linked increases in daily temperature with adverse outcomes, including mortality and hospital admissions (Anderson and Bell, 2009; Bell et al., 2008; McMichael et al., 2008). Most global climate models are predicting significant increases over the next few decades in both average temperatures and in the frequency and duration of heat waves. For example, The United Nations Intergovernmental Panel on Climate Change (IPCC) has predicted that global surface temperature is likely to rise between 1.1 and 6.4 1C (2.0–11.5 1F) during the 21st century (IPCC, 2007). Given these projected changes, it is important to attempt to provide estimates of the direct impact of heat stress on public health. While there are many uncertainties involved in quantifying these impacts, there is still merit in generating crude estimates and also in examining the key assumptions and factors that alter these estimates. Several health impact assessments have been conducted for common urban air pollutants such as particulate matter (PM) and ozone. For example, Ostro and Chestnut (1998) generated esti- mates of the health benefits associated with the U.S. Environ- mental Protection Agency’s proposed standards for PM 2.5 (PM less than 2.5mm in diameter), while Kunzli et al. (2000) estimated the potential health benefits associated with reducing traffic-related PM in three European countries. Similarly, Deck et al. (2001) estimated the health benefits associated with attaining U.S. PM 2.5 standards in two U.S. cities. Estimates of health effects have been developed for 26 cities in 12 European countries (APHEIS, 2001), and applying dose–response information primarily from the industrialized nations, the World Bank estimated the benefits of air pollution control in Mexico City (World Bank, 2002). A more recent health impact assessment estimated the national benefits of attaining the U.S. Environmental Protection Agency  s ozone standard (Hubbell et al., 2005). Additional guidance for estimating the health effects of air pollution has been provided by the World Health Organization (WHO, 2001) and by the National Research Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/envres Environmental Research 0013-9351/$ - see front matter & 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.envres.2011.08.013 n Corresponding author at: Centre for Research in Environmental Epidemiology, Barcelona 08019, Spain. E-mail address: Bostro@Creal.cat (B. Ostro). Environmental Research 111 (2011) 1258–1264