Guest Post by Kip Hansen

Science is a wonderful thing. As time moves on, in a single direction, Science, as an endeavor, discovers new things and improves our lives.

With a “hat tip” to the inestimable Jane Brody, health journalist at the NY Times who covers the story here, we are reminded of the study [free .pdf] from Antonio Gasparrini et al. which was published in The Lancet, July 25, 2015, with the [way too long] title: “Mortality risk attributable to high and low ambient temperature: a multicountry observational study”.

The bottom-line finding, the take home message, might surprise even readers here at WUWT, quoted in the side-bar of the journal article:

Interpretation:

We report that non-optimum ambient temperature is responsible for substantial excess in mortality, with important differences between countries. Although most previous research has focused on heat-related effects, most of the attributable deaths were caused by cold temperatures. Despite the attention given to extreme weather events, most of the effect happened on moderately hot and moderately cold days, especially moderately cold days. This evidence is important for improvements to public health policies aimed at prevention of temperature-related health consequences, and provides a platform to extend predictions on future effects in climate-change scenarios. [extra emphasis mine – kh]

It is not extreme weather, not extreme temperatures, neither hot or cold, that cause the most temperature-related deaths:

“The underlying physiopathological mechanisms that link exposure to non-optimum temperature and mortality risk have not been completely elucidated. Heat stroke on hot days and hypothermia on cold days only account for small proportions of excess deaths.

“Discussion

Our findings show that temperature is responsible for advancing a substantial fraction of deaths, corresponding to 7.71% of mortality in the selected countries within the study period. Most of this mortality burden was caused by days colder than the optimum temperature (7.29%), compared with days warmer than the optimum temperature (0.42%). Furthermore, most deaths were caused by exposure to moderately hot and cold temperatures, and the contribution of extreme days was comparatively low, despite increased RRs [relative risks].

Our results suggest that public-health policies and adaptation measures should be extended and refocused to take account of the whole range of effects associated with temperature…”

The oft-repeated mantra of “global warming will cause more heat waves, extremely high temperature days, which kill more people” is simply not true — heat waves are not the big killer. Rather, cold days are the big killer – but not extremely cold days, as we intuitively think, but moderately cold days are responsible for the highest percentage of excess deaths due to ambient temperature. Equally true, it is not the extremely hot days that cause the bulk of high ambient temperature related deaths, but moderately hot days.

Read the study, [corrected now, h/t Griff and Les Johnson] it is short and accessible.

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Anthony: I’ve updated the title and I thought it important to display this graph of results, thanks to reader “Greg”. From the paper:

More temperature-attributable deaths were caused by cold (7·29%, 7·02–7·49) than by heat (0·42%, ·39–0·44). Extreme cold and hot temperatures were responsible for 0·86% (0·84–0·87) of total mortality.

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