Title, Date of Publication & Journal

‘Climate change effects on human health: projections of temperature-related mortality for the UK during the 2020s, 2050s and 2080s’

Hajat S, et al. Journal of Epidemiology and Community Health, 2013;0:1–8. doi:10.1136/jech-2013-202449

Claim supported by evidence?

The paper supports the suggestion that more people in the UK will die due to heat and to cold over the next seven decades, based on predicted changes in climate and in population size and structure. 

However, this predicted increase in number of deaths is due entirely to increasing population sizes and increasing proportions of elderly people (the group most vulnerable to temperature extremes).  It is not due to climate change.

Summary

Taking into account predicted changes in climate (from Met Office Hadley Centre predictions), the overall RATE of deaths due to temperature extremes in the UK is predicted to decrease (see Figure 4 and Table 1) – this is due to a decrease in the RATE (deaths per 100,000 people) of people dying from cold more than offsetting an increase in the rate of people dying from heat.

BUT the absolute NUMBERS of people dying from both heat and cold is predicted to increase due to increasing population size and an increase in the proportion of elderly people in the UK population (based on ONS figures and predictions).

In other words:

• The population is expected to get bigger and older by the 2080s. 
• This means more people will die overall – the absolute numbers of deaths from extreme temperature will be higher than they are now.
• But that increase in deaths is not as a result of a warmer UK.
• In fact, for any individual within that population the risk of death from extreme temperature is lower than it would be with today’s climate conditions.
• That’s because the rate of increase in heat deaths is more than offset by the rate of decrease in cold deaths under these climate and population predictions.

Study Conclusions

In absolute numbers, more people will still die of cold than will die of heat in 2080 so cold will still be the highest burden.

For an individual the decrease in risk of dying due to cold more than offsets the increase in risk of dying due to heat.

But due to population growth more people will die due to temperature extremes as a whole in 2080 than they do now.

Strengths/Limitations

Strengths:

The authors used sensible predictions of population changes (from the ONS) and for climate change (from the Met Office Hadley Centre)

Limitations:

The summary and press release fail to adequately separate effects of projected population growth from effects of projected climate change.

Glossary

ONS = Office for National Statistics