title: Variability in temperature-related mortality projections under climate change.
abstract: BACKGROUND
  Most studies that have assessed impacts on mortality of future temperature increases have relied on a small number of simulations and have not addressed the variability and sources of uncertainty in their mortality projections.
  
  
  OBJECTIVE
  We assessed the variability of temperature projections and dependent future mortality distributions, using a large panel of temperature simulations based on different climate models and emission scenarios.
  
  
  METHODS
  We used historical data from 1990 through 2007 for Montreal, Quebec, Canada, and Poisson regression models to estimate relative risks (RR) for daily nonaccidental mortality in association with three different daily temperature metrics (mean, minimum, and maximum temperature) during June through August. To estimate future numbers of deaths attributable to ambient temperatures and the uncertainty of the estimates, we used 32 different simulations of daily temperatures for June-August 2020-2037 derived from three global climate models (GCMs) and a Canadian regional climate model with three sets of RRs (one based on the observed historical data, and two on bootstrap samples that generated the 95% CI of the attributable number (AN) of deaths). We then used analysis of covariance to evaluate the influence of the simulation, the projected year, and the sets of RRs used to derive the attributable numbers of deaths.
  
  
  RESULTS
  We found that < 1% of the variability in the distributions of simulated temperature for June-August of 2020-2037 was explained by differences among the simulations. Estimated ANs for 2020-2037 ranged from 34 to 174 per summer (i.e., June-August). Most of the variability in mortality projections (38%) was related to the temperature-mortality RR used to estimate the ANs.
  
  
  CONCLUSIONS
  The choice of the RR estimate for the association between temperature and mortality may be important to reduce uncertainty in mortality projections.
authors.affiliation: Département de santé environnementale et santé au travail (DSEST), Université de Montréal, Montréal, Québec, Canada.
authors.forename: Tarik
authors.initials: T
authors.lastname: Benmarhnia
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Sottile
authors.forename: Céline
authors.initials: C
authors.lastname: Plante
authors.forename: Allan
authors.initials: A
authors.lastname: Brand
authors.forename: Barbara
authors.initials: B
authors.lastname: Casati
authors.forename: Michel
authors.initials: M
authors.lastname: Fournier
authors.forename: Audrey
authors.initials: A
authors.lastname: Smargiassi
mesh_terms: D002423:Cause of Death / Q000639:trends; D057231:Climate Change; D018882:Heat Stress Disorders / Q000401:mortality*; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D008962:Models, Theoretical; D011237:Predictive Value of Tests