A study by Pierre Masselot's team published a few weeks ago in The Lancet compares excess mortality attributed to heat and cold in 854 cities in Europe.
Over the period 2000-2019, it shows in particular that excess mortality attributable to cold is overall 10 times higher than that attributed to heat in Europe: for 203,620 deaths attributed to cold, only 20,173 deaths would have been caused by heat during this period. period.
According to this study, we could deduce that the Urban Heat Island (UHI) effect would therefore be generally beneficial since it would tend to reduce excess mortality caused by the cold in cities. This would particularly be the case in London, where the risk of mortality doubles during cold spells.
Except that the Lancet study excluded the heatwave of August 2003!
This heatwave alone caused around 70,000 deaths in Europe.
We can therefore question the conclusions that can be drawn from this study in terms of evaluating the impacts of the urban heat island on excess mortality in Europe, which remains generally underestimated.
In a future post I will discuss the case of Paris, which is the city where excess mortality linked to heat is the highest according to this study, even without considering the heatwave of 2003.
For the story, the formula “Heat island = death island?” was first used in 1972 by American epidemiologists Robert W. Buechley, John van Bruggen and Lawrence E. Truppi in a seminal article on the ICU study.
Sources:
- Lancet chart and study
- Figures from the 2003 heatwave
- “Heat island = death island? »
Image: The Lancet, Annual rates crude mortality due to cold (left) and heat (right) by country, broken down by age group (note that the legend on the abscissa is different between the left and the right).