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Dying from Cold Spells in Subtropical China

Paper Reviewed
Zhou, M.G., Wang, L.J., Liu, T., Zhang, Y.H., Lin, H.L., Luo, Y., Xiao, J.P., Zeng, W.L., Zhang, Y.W., Wang, X.F., Gu, X., Rutherford, S., Chu, C. and Ma, W.J. 2014. Health impact of the 2008 cold spell on mortality in subtropical China: the climate and health impact national assessment study (CHINAs). Environmental Health 13: 10.1186/1476-069X-13-60.

In introducing their study of cold-induced deaths associated with the unusually long cold spell of January and February 2008 - when fifteen provinces of subtropical southern China experienced temperatures that were 2-4°C lower than those of the same time period of neighboring years - Zhou et al. (2014) note that this temperature aberration was considered to be "a once in 50-100 years event," which they felt provided an especially unique opportunity to study the health effects of relative coldness on human mortality.

Thirty-six communities were selected for study, 12 of which were in urban areas and 24 of which were in rural areas. They were located in 4 geographical regions that included 15 municipalities or provinces, which were home to 784 million inhabitants. And after the appropriate data were acquired and analyzed, the fourteen researchers found that the cold spell increased mortality by a whopping 43.8% compared to non-cold spell days. They also report that "effects were more pronounced for respiratory mortality than for cardiovascular or cerebrovascular mortality, for females more than for males, and for the elderly aged ≥75years old more than for younger people." And they say that "overall, 148,279 excess deaths were attributable to the 2008 cold spell," which effect they note was "mainly from extreme low temperatures rather than sustained cold days during the 2008 cold spell."

As for the ramifications of their work, Zhou et al. say their findings imply "it is necessary to develop adaptive plans for cold spells even in subtropical regions, where populations are generally most acclimatized to hot weather both biologically and behaviorally, but more sensitive to cold weather due to lower adaptive capacity." In addition, we are always wont to remind everyone that the global warming of the past century was due more to the rising of daily minimum temperatures than to the rising of daily maximum temperatures, the former of which have been shown by Karl et al. (1984, 1991) to have risen at a rate that was fully three times greater than the latter, which should definitely tend to reduce total temperature-induced mortality throughout the world.

References
Karl, T.R., Jones, P.D., Knight, R.W., Kukla, G., Plummer, N., Razuvayev, V., Gallo, K.P., Lindseay, J., Charlson, R.J. and Peterson, T.C. 1984. A new perspective on recent global warming: asymmetric trends of daily maximum and minimum temperature. Bulletin of the American Meteorological Society 74: 1007-1023.

Karl, T.R., Kukla, G., Razuvayev, V.N., Changery, M.J., Quayle, R.G., Heim Jr., R.R., Easterling, D.R. and Fu, C.B. 1991. Global warming: evidence for asymmetric diurnal temperature change. Geophysical Research Letters 18: 2253-2256.

Posted 25 November 2014