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Dying from Heat and Cold in China: Which is the Greater Killer?
Wu, W., Xiao, Y., Li, G., Zeng, W., Lin, H., Rutherford, S., Xu, Y., Luo, Y., Xu, X., Chu, C. and Ma, W. 2013. Temperature-mortality relationship in four subtropical Chinese cities: A time-series study using a distributed lag non-linear model. Science of the Total Environment 449: 355-362.

The authors note that "numerous studies have reported the association between ambient temperature and mortality," but they say that "few multi-city studies have been conducted in subtropical regions in developing countries." Hence, they proceed to atone for this neglect.

What was done
Wu et al. first assessed the health effects of temperature on mortality in four subtropical cities of China (Changsha, Kunming, Guangzhou and Zhuhai) by means of a "double threshold-natural cubic spline" distributed lag non-linear model at different temporal lags, after which they used the combined results to conduct a meta-analysis to estimate the overall cold and hot effects on mortality at different lag days.

What was learned
The eleven researchers report that a U-shaped relationship between temperature and mortality was found in the four cities, which is indicative of the fact that "mortality is usually lowest around a certain temperature and higher at lower or higher temperatures," as they say has also been found to be the case by Alberdi et al. (1998), Huynen et al. (2001), Curriero et al. (2002), O'Neill et al. (2003), Armstrong (2006), Laaidi et al. (2006) and Kan et al. (2007). In addition, they found that "the hot effect peaked at the current day, and then diminished with lag days; whereas "the cumulative cold effect increased gradually with lag days, with the highest effect at lag0-27."

What it means
Although "both low and high temperatures were associated with increased mortality in the four subtropical Chinese cities," according to Wu et al., they indicate that the "cold effect was more durable and pronounced than the hot effect." And these observations clearly indicate that global warming leads to a net reduction in human mortality, which is just the opposite of what many climate alarmists and governmental agencies (like the U.S. Environmental Protection Agency) are trying to get everyone to believe.

Alberdi, J.C., Diaz, J., Montero, J.C., and Miron, I. 1998. Daily mortality in Madrid community 1986-1992: relationship with meteorological variables. European Journal of Epidemiology 14: 571-578.

Armstrong, B. 2006. Models for the relationship between ambient temperature and daily mortality. Epidemiology 17: 624-631.

Curriero, F.L., Heiner, K.S., Samet, J.M., Zeger, S.L., Strug, L. and Patz, J.A. 2002. Temperature and mortality in 11 cities of the eastern United States. American Journal of Epidemiology 155: 80-87.

Huynen, M.M., Martens, P., Schram, D., Weijenberg, M.P. and Kunst, A.E. 2001. The impact of heat waves and cold spells on mortality rates in the Dutch. Environmental Health Perspectives 109: 463-470.

Kan, H., London, S.J., Chen, H., Song, G., Chen, G., Jiang, L. et al. 2007. Diurnal temperature range and daily mortality in Shanghai, China. Environmental Research 103: 424-431.

Laaidi, M., Laaidi, K. and Besancenot, J.P. 2006. Temperature-related mortality in France, a comparison between regions with different climates from the perspective of global warming. International Journal of Biometeorology 51: 145-153.

O'Neill, M.S., Zanobetti, A. and Schwartz, J. 2003. Modifiers of the temperature and mortality association in seven US cities. American Journal of Epidemiology 157: 1074-1082.

Reviewed XX August 2013