Christidis, N., Donaldson, G.C. and Stott, P.A. 2010. Causes for the recent changes in cold- and heat-related mortality in England and Wales. Climatic Change 102: 539-553.
The authors write that "the IPCC AR4 states with very high confidence that climate change contributes to the global burden of disease and to increased mortality," citing the contribution of Confalonieri et al. (2007) to that document.
What was done
In an effort handsomely suited to evaluate this very-high-confidence contention of the IPCC, Christidis et al. extracted the numbers of daily deaths from all causes from death registration data supplied by the UK Office of National Statistics for men and women fifty years of age or older in England and Wales for the period 1976-2005, which they divided by daily estimates of population "obtained by fitting a fifth order polynomial to mid-year population estimates, to give mortality as deaths per million people," after which they compared the death results with surface air temperature data that showed a warming trend during the same three-decade period of 0.47°C per decade. In addition, they employed a technique called optimal detection, which they describe as "a formal statistical methodology" that can be used to estimate the role played by human adaptation in the temperature-related changes in mortality they observed.
What was learned
As expected, during the hottest portion of the year, warming led to increases in death rates, while during the coldest portion of the year it lead to decreases in death rates. More specifically, the three scientists report that if no adaptation had taken place, there would have been 1.6 additional deaths per million people per year due to warming in the hottest part of the year over the period 1976-2005, but there would have been 47 fewer deaths per million people per year due to warming in the coldest part of the year, for a lives-saved to life-lost ratio of 29.4, which represents a huge net benefit of the warming experienced in England and Wales over the three-decade period of warming. And when adaptation was included in the analysis, as was the case in the data they analyzed, they found there were only 0.7 death per million people per year due to warming in the hottest part of the year, but a decrease of fully 85 deaths per million people per year due to warming in the coldest part of the year, for a phenomenal lives-saved to life-lost ratio of 121.4.
What it means
Clearly, the IPCC's "very-high-confidence" conclusion is woefully wrong. Warming is highly beneficial to human health, even without any overt adaptation to it. And when adaptations are made, warming is incredibly beneficial in terms of lengthening human life span.
For more on this important topic, including results from all around the world, see the many items we have archived under the subheadings of Health Effects (Temperature) in our Subject Index.
Confalonieri, U., Menne, B., Akhtar, R., Ebi, K.L., Hauengue, M., Kovats, R.S., Revich, B. and Woodward, A. 2007. Human health. In: Parry, M.L. et al. (Eds.) Climate Change 2007: Impacts, Adaptation and Vulnerability. Cambridge University Press, Cambridge, United Kingdom.