Is a major new report about “the health effects of climate change” that describes “Climate” as the “biggest health threat” for the 21st century actually based upon a convenient forgetfulness of parts of the literature, and the scientific equivalent of chinese whispers?
It may never be possible to answer that question in full and in full confidence. But there is one interesting, major detail that relates to something I just blogged about.
Today (May 14) the “Lancet and University College London Institute for Global Health Commission” launched a report titled “Managing the health effects of climate change” (Lancet 2009; 373: 1693–733).
I looked at the report in terms of cold- and warm-weather related deaths and this is what I have found:
The Lancet/UCL 2009 report’s claim that warming is worse than cooling is based on a single book chapter from 2003 that forgets to mention two very relevant articles; and that disregards exactly the effect used in one of those two articles to demonstrate that cooling is worse than warming.
Here’s how I started: having had read that at least in Europe, cooling kills more than warming, I looked with interest for any mention of that aspect in the report. My search brought me to page 9:
From a conservative perspective, although a minority of populations might experience health benefits (mostly related to a reduction in disease related to cold weather), the global burden of disease and premature death is expected to increase progressively.(ref. 16)
That looked like a peculiar statement indeed: sporting a reference to “health benefits” for the few (all of them, in Europe?), but suddenly making warming a bigger killer than cooling on a global scale.
When was all of that discovered, I wondered? Thankfully, I could find reference 16 on the web:
16. Campbell-Lendrum DH, Corvalán CF, Prüss Ustün A. How much disease could climate change cause? In: McMichael AJ, Campbell-Lendrum DH, Corvalan CF, et al, eds. Climate change and human health: risks and responses. Geneva: WHO, 2003.
Relevant quotes from Campbell-Lendrum DH et al. (curiously, again from page 9):
[…] Direct physiological effects of heat and cold on cardiovascular mortality – Strength of evidence
The association between daily variation in meteorological conditions and mortality has been described in numerous studies from a wide range of populations in temperate climates (16, 17). These studies show that exposure to temperatures at either side of a “comfort range” is associated with an increased risk of (mainly cardio-pulmonary) mortality.
Given the limited number of studies on which to base global predictions, quantitative estimates are presented only for the best supported of the direct physiological effects of climate change—changes in mortality attributable to extreme temperature for one or several days. For cold and temperate regions, a relationship from a published study was used (24) […]
The mystery was just deepening, with people suddenly dying not because of warmth or cold, but due to daily meteorological changes, and in particular because of “exposure to temperatures” outside of a “comfort range”.
It was time then to take a look at what those numerical references were about:
16. Alderson, M.R. Season and mortality. Health Trends 17: 87–96 (1985).
17. Green, M.S. et al. Excess winter-mortality from ischaemic heart disease and stroke during colder and warmer years in Israel. European Journal of Public Health 4: 3–11 (1994).
24. Kunst, A. et al. Outdoor air temperature and mortality in the Netherlands—a time series analysis. American Journal of Epidemiology 137(3): 331–341 (1993).
And what was even more notable were the “forgotten” references:
- Keatinge, W.R. et al., Heat related mortality in warm and cold regions of Europe: observational study. BMJ 2000;321:670-673 ( 16 September )
- Donaldson, G.C. and Keatinge, W.R. Excess winter mortality: influenza or cold stress? Observational study. BMJ 2002;324:89-90 ( 12 January )
In summary: the Lancet/UCL 2009 report claims warming is worse than cooling on the basis of a single book chapter from 2003 that mentions: a very old article from 1985; a 1993 research on Israel; a single 1994 article about the Netherlands to represent “cold and temperate regions“.
And that very same single book chapter avoids any reference to two much more recent works, form 2000 and 2002, covering the whole of Europe, and pointing in the direction of…cooling being worse than warming.
The “forgotten references” from 2002 may as well have been unknown to the authors of the 2003 book chapter. But that is no excuse for the authors of the 2009 report.
Also, the fact that those articles were forgotten is obviously due to pure chance: because otherwise, it would be an unfortunate case of “foul play in citation“, a.k.a.“bibliographic negligence” or “citation amnesia“.
But that was not all. Here a bit more from Campbell-Lendrum DH et al. (2003):
There also is evidence for a “harvesting effect”, i.e. a period of unusually lower mortality following an extreme temperature period. This indicates that in some cases extreme temperatures advance the deaths of vulnerable people by a relatively short period, rather than killing people who would otherwise have lived to average life expectancy. However, this effect has not been quantified for temperature exposures and is not included in the model. As there is large uncertainty about the number of years that the casualties would have lived (i.e. the attributable years which are lost by exposure to the risk factor) the relative risk estimates will be used to calculate only attributable deaths, not DALYs. […]
That is not the way Keatinge WR et al (2000) presented their results three years before:
Some of those who died in the heat may not have lived long if a heat wave had not occurred. Mortality often falls below baseline for several days after the end of a heat wave, and this has been interpreted as indicating that some of the people dying during the heat wave were already close to death.
[…] Falls in temperature in winter are closely followed by increased mortality, with characteristic time courses for different causes of death. The increases are of sufficient size to account for the overall increase in mortality in winter, suggesting that most excess winter deaths are due to relatively direct effects of cold on the population.“
Campbell-Lendrum DH et al. (2003) may as well have had a disagreement with Keatinge WR et al (2000): but if that were the case, they should have referenced to it and discussed however briefly the reasons for their disagreement. And of course the authors of the 2009 report should have included some remarks on why they would care not a bit about the “harvesting effect”, since the…effect of that effect directly relates to people’s health (well, it kills them…)
In summary: the Lancet/UCL 2009 report claims warming is worse than cooling on the basis of a single book chapter from 2003 that disregards the “harvesting effect”, the very same effect used in a 2000 article to demonstrate that cooling is worse than warming.
It looks as if the information was available out there, but reached the authors of the 2009 report distorted by the opinion of the 2003 book chapter’s authors . One may be forgiven to equate that with a game of..Chinese whispers (a.k.a. Telephone)!
Obviously there are so many claims one can investigate.
But the fact that I was able in a few minutes to identify what are potentially major flaws in the estimation of the net benefits of CO2, suggests that more problems may lurk somewhere else, in the Lancet/UCL report.