More deaths due to climate change? Or maybe not.

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Coverage of a paper just published by Journal of Epidemiology and Community Health included dramatic headlines such as the Guardian's Heat-related deaths in the UK will rise 257% by 2050 because of climate change. But a closer look at the numbers in the paper paints a rather different picture.

Figure 4 of the paper shows the number of deaths expected per 100,000 people in each category, and how the authors estimate this will change into the 2080s.


But the vertical axes for the two plots are different, and they should perhaps have been drawn like this.


Or even added in a 'combined plot' [added 6th February 2013]


This clearly reveals that, in terms of rate per 100,000, the decline in cold-related death rate easily outweighs the increase in the heat-related death rate. So overall, for any individual in the UK, the risk of a temperature-related death is expected to fall steadily due to climate change. Bring it on!

But since there are going to be more old people in the future, the absolute numbers of deaths is going to increase - and this number was emphasised by the authors and got the headlines.

The abstract of the paper includes the phrase "The increased number of future temperature-related deaths was partly driven by projected population growth and ageing." According to the projections in the paper, if the population make-up did not change, the overall mortality risk would go down. So it would have been more accurate to say "The increased number of future temperature-related deaths was wholly driven by projected population growth and ageing.".

But that is clearly not the message that the authors wanted to convey. It is unfortunate that this kind of presentation gives ammunition to those who say that the effects of climate change are being exaggerated.


Here is the article's Results:

" A significantly raised risk of heat-related and cold-related mortality was observed in all regions. The elderly were most at risk. In the absence of any adaptation of the population, heat-related deaths would be expected to rise by around 257% by the 2050s from a current annual baseline of around 2000 deaths, and cold-related mortality would decline by 2% from a baseline of around 41 000 deaths. The cold burden remained higher than the heat burden in all periods. The increased number of future temperature-related deaths was partly driven by projected population growth and ageing. "

So, we have an increase in heat deaths of 5000 and a decrease in cold deaths of about 800. Not fortunate!

Also, UK latitude is a colder weather one. Warmer latitudes will increase heat deaths/cold deaths in even greater proportions

It's the switch from rates to absolute numbers that's crucial here. The media (and academics keen to attract media interest) may indeed focus on headline-grabbing absolute _numbers_ of deaths, but action by policy-makers must be based on the appropriate metric, which in this case is the _rate_ of death (eg per 100,000). I think we can all agree that it would make no sense for politicians to demand urgent action over the current soaring _number_ of deaths of those aged over 100 compared to the number of such deaths in the 1950s....

Dear David As the author of the paper, I would like to stress that all our findings are explicit in the full paper and there is no agenda to convey anything other than what the data show. Regarding the abstract, temperature-related deaths are partly driven by demographic changes but not completely - when these demographics are held constant (which is clearly not realistic in any case) we still estimated a 169% increase in heat deaths by the 2050s. It's true that there would be a greater reduction in cold deaths, but this shouldn't detract from the need to reduce the burden from both hot and cold weather. I think it is better to consider the 2 impacts separately - in much the same why that a reduction in deaths from one form of cancer wouldn't mean that we do not need to worry about an increase in another cancer type. That's why the combined graph above is oversimplifying the issue. Remember also that we were only assessing one type of health impact of climate change - there are likely to be many others, so 'bring it on' may not be the best response. Shakoor

Thanks for this: I agree that it is good to consider the impacts separately, but 'temperature-related deaths', to my understanding, refers to deaths from both hot and cold temperature. Otherwise they are 'heat-related-deaths' or some other phrase. Both are being considered, but all the prominence is given to just one outcome measure. David

This is another example of climate astrology - based on computer modeled assumptions - we don't actually know whether it will be cooler of hotter in the 2050s, or what else might have happened to the earth - so I find this sort of one-sided prediction paper rather pointless.