The burden of the ‘urban heat-island’ effect falls most heavily on economically disadvantaged neighborhoods.

The brunt of a city’s heat is often borne by residents of low-income neighbourhoods, according to an analysis of large urban areas around the world.

The bustle and buildings in a city generally make it hotter than the surrounding countryside. To investigate the impact of this ‘urban heat-island’ effect, Angel Hsu at Yale-NUS College in Singapore and her colleagues studied satellite and census data for 25 cities on 5 continents.

In 18 of those cities, the burden of urban heat fell more heavily on less affluent neighbourhoods than on richer districts. The cities with this disproportionate burden ranged from Berlin to Buenos Aires.

The analysis also found that neighbourhoods where plant life is sparse tended to be warmer than districts with lush vegetation. Adding green spaces to lower income areas could help to relieve this inequality, the authors say.