Differential and combined impacts of extreme temperatures and air pollution on human mortality in south–central Canada. Part II: future estimates

Abstract

This paper forms the second part of an introduction to a synoptic weather typing approach to assess differential and combined impacts of extreme temperatures and air pollution on human mortality, focusing on future estimates. A statistical downscaling approach was used to downscale daily five general circulation model (GCM) outputs (three Canadian and two US GCMs) and to derive six-hourly future climate information for the selected cities (Montreal, Ottawa, Toronto, and Windsor) in south-central Canada. Discriminant function analysis was then used to project the future weather types, based on historical analysis defined in a companion paper (Part I). Future air pollution concentrations were estimated using the within-weather-type historical simulation models applied to the downscaled future GCM climate data. Two independent approaches, based on (1) comparing future and historical frequencies of the weather groups and (2) applying within-weather-group elevated mortality prediction models, were used to assess climate change impacts on elevated mortality for two time windows (2040-2059 and 2070-2089). Averaging the five GCM scenarios, across the study area, heat-related mortality is projected to be more than double by the 2050s and triple by the 2080s from the current condition. Cold-related mortality could decrease by about 45-60% and 60-70% by the 2050s and the 2080s, respectively. Air pollution-related mortality could increase about 20-30% by the 2050s and 30-45% by the 2080s, due to increased air pollution levels projected with climate change. The increase in air pollution-related mortality would be largely driven by increases in ozone effects. The population acclimatization to increased heat was also assessed in this paper, which could reduce future heat-related mortality by 40%. It is most likely that the estimate of future extreme temperature-and air pollutionrelated mortality from this study could represent a bottomline figure since many of the factors (e.g., population growth, age structure changes, and adaptation measures) were not directly taken into account in the analyses.

Projections of mid-century summer air-quality for North America: effects of changes in climate and precursor emissions

“…Makar et al, 2009) and ozone deposition (Engardt, 2008;Van Dingenen et al, 2009;Stella et al, 2011). The human-health impact of air pollution is one of the main drivers behind research in this field, with potentially substantial health effects resulting from climatechange-induced changes in air-quality (Sheffield et al, 2011;Chang et al, 2010;Tagaris et al, 2009Tagaris et al, , 2010Cheng et al, 2009;Jackson et al, 2010). Global financial losses due to reductions in crop yields resulting from ozone deposition are expected to reach between $1 billion to $17 billion, depending on the emissions scenario employed (Averny et al, 2011).…”

Differential and combined impacts of extreme temperatures and air pollution on human mortality in south–central Canada. Part I: historical analysis

“…Within-decile mean mortality residuals in the bottom deciles were usually lower than those of the top deciles for all pollutants except for CO. In addition to this decile analysis, within-"other"-weather-group regression results also show that only air pollutants other than weather variables are significantly associated with elevated mortality, with a model R 2 of 0.71, 0.62, 0.40, and 0.30 for Montreal, Ottawa, Windsor and Toronto, respectively (refer to a companion paper-Part II, Cheng et al 2009 for details on regression). This finding is consistent with that of previous studies (Lambert et al 1998;Toronto Public Health 2001;Vedal et al 2003), which concluded that 1954 1959 1964 1969 1974 1979 1984 1989 1994 Fig.…”

“…The study could enhance our understanding of environmental problems related to human health. To support the recommendation of adaptation policies to reduce risks to vulnerable populations due to climate change, it is necessary to estimate possible changes in future extreme temperature-and air pollution-related mortality, which is the major objective of a companion paper (Part II, Cheng et al 2009). …”

“…This method promises to evaluate relationships among a variety of weather elements rather than only individual variablesthe synergistic impact of several elements being more significant than the sum of their individual impacts (Kalkstein 1991;Pope and Kalkstein 1996;. Part of the current study focusing on climate change impacts analysis on both future air pollution-and temperature extreme-related mortality in south-central Canada is presented in a companion paper (Part II, Cheng et al 2009). To effectively estimate climate change-induced future elevated mortality, historical analysis is essential for us to build a solid science foundation on health impacts of air pollution and extreme temperatures.…”

Safety index of heat wave mortality using big data

“…Notwithstanding this notion, most projections of heat wave damages have previously been derived from the statistics of excess deaths based on observed data for vulnerable regions. Based on these predictions, a substantial increase in excess deaths has been deduced for the United States [21], Canada [22], Europe [23], United Kingdom [24], Australia [25], and other regions globally. Most of these studies, however, have not considered the aging demographics and related increases in heat vulnerability.…”