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Childhood Diarrhea: What's Diurnal Temperature Range Got to Do with It?
Xu, Z., Huang, C., Turner, L.R., Su, H., Qiao, Z. and Tong, S. 2013. Is diurnal temperature range a risk factor for childhood diarrhea? PLoS One 8: e64713.

The authors write that "previous studies have found that high and cold temperatures increase the risk of childhood diarrhea," but they say that much less is known about whether the within-day variation of temperature (i.e., the daily maximum minus minimum, or diurnal temperature range, DTR) has any effect on it. And so they decided to find out for themselves.

What was done
In the words of Xu et al., "a Poisson generalized linear regression model combined with a distributed lag non-linear model was used to examine the relationship between diurnal temperature range and emergency department admissions for diarrhea among children under five years in Brisbane [Australia] from 1st January 2003 to 31st December 2009."

What was learned
The six scientists say "there was a statistically significant relationship between diurnal temperature range and childhood diarrhea," such that "a 1°C increase in diurnal temperature range was associated with a 3% increase of Emergency Department Admissions for childhood diarrhea."

What it means
Xu et al. conclude that "as climate change continues, DTRs are likely to become more variable," and as a result, they say that "the incidence of childhood diarrhea may increase." However, this is likely not the case; for Karl et al. (1984, 1991) have shown that over the course of the bulk of 20th century global warming, daily minimum temperatures rose at a rate fully three times greater than daily maximum temperature over most of the world. And this observation means that DTRs have actually declined over this period, and must have led to significant decreases in emergency department admissions for diarrhea among children under five years of age, which is actually something for which we could thank global warming.

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.

Reviewed 16 October 2013