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Estimation and uncertainty analysis of impacts of future heat waves on mortality in the eastern United States - PubMed

Estimation and uncertainty analysis of impacts of future heat waves on mortality in the eastern United States

Jianyong Wu et al. Environ Health Perspect. 2014 Jan.

Abstract

Background: Climate change is anticipated to influence heat-related mortality in the future. However, estimates of excess mortality attributable to future heat waves are subject to large uncertainties and have not been projected under the latest greenhouse gas emission scenarios.

Objectives: We estimated future heat wave mortality in the eastern United States (approximately 1,700 counties) under two Representative Concentration Pathways (RCPs) and investigated sources of uncertainty.

Methods: Using dynamically downscaled hourly temperature projections for 2057-2059, we projected heat wave days that were defined using four heat wave metrics and estimated the excess mortality attributable to them. We apportioned the sources of uncertainty in excess mortality estimates using a variance-decomposition method.

Results: Estimates suggest that excess mortality attributable to heat waves in the eastern United States would result in 200-7,807 deaths/year (mean 2,379 deaths/year) in 2057-2059. Average excess mortality projections under RCP4.5 and RCP8.5 scenarios were 1,403 and 3,556 deaths/year, respectively. Excess mortality would be relatively high in the southern states and eastern coastal areas (excluding Maine). The major sources of uncertainty were the relative risk estimates for mortality on heat wave versus non-heat wave days, the RCP scenarios, and the heat wave definitions.

Conclusions: Mortality risks from future heat waves may be an order of magnitude higher than the mortality risks reported in 2002-2004, with thousands of heat wave-related deaths per year in the study area projected under the RCP8.5 scenario. Substantial spatial variability in county-level heat mortality estimates suggests that effective mitigation and adaptation measures should be developed based on spatially resolved data.

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Conflict of interest statement

The authors declare they have no actual or potential competing financial interests.

Figures

Figure 1
Figure 1

Baseline (2002–2004; A,D) and future (2057–2059; B,C,E,F) estimates of heat wave frequency and duration in study area counties. Heat wave frequency and duration estimates are integrated averages based on four heat wave metrics.

Figure 2
Figure 2

Projected county-level excess deaths [means (A,B) and SDs (C,D)] due to heat waves in 2057–2059 under RCP4.5 (A,C) and RCP8.5 (B,D) scenarios. The excess deaths for each scenario are average estimates obtained using four heat wave metrics and four population projections.

Figure 3
Figure 3

Probability distribution of annual excess mortality attributable to heat waves in the study domain under RCP4.5, RCP8.5, and the two scenarios combined. Data shown were derived from pooling the total excess deaths under all possible situations considered in this study, including two temperature calibration methods, four heat wave definitions, four population projections, 3 years, and nine sets of AR values.

Figure 4
Figure 4

Sensitivity analysis of annual heat wave mortality affected by various factors. The factor with a higher Si value has higher influence on estimated the excess mortality. Abbreviations: RR, the relative risk of heat wave days to non–heat wave days; calibration, calibration ratio interpolation methods; HWM, heat wave metrics; RCP, RCP scenarios.

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