Sussex – The ‘urban heat island’ effect could make climate change costs for cities at least twice as high as the rest of the world. But simple measures such as installing cool pavements and roofs could cut those costs.

An international team of economists from the world’s major cities have published the first study quantifying the potentially devastating combined impact of global and local climate change on urban economies. 

The analysis of 1,692 cities shows that the total economic costs of climate change for cities this century could be 2.6 times higher when heat island effects are taken into account than when they are not, according to a statement from the University of Sussex. For those cities hit hardest, losses could reach 10.9 per cent of GDP by 2100, compared with a global average of 5.6 per cent.

The urban heat island occurs when natural surfaces, such as vegetation and water, are replaced by heat-trapping concrete and asphalt, and is exacerbated by heat from cars, air conditioners and so on. 

Not only is it expected to add a further two degrees to global warming estimates for the most populated cities by 2050, it also damages urban economies: more energy is required for cooling, air is more polluted, water quality decreases and workers are less productive, to name a few. 

Measures that could limit the high economic and health costs of rising urban temperatures are therefore a major priority for policy makers.

The research team found that the cheapest measure to reduce the urban heat island effect is a moderate-scale installation of cool pavements and roofs. Changing just 20 per cent of a city’s roofs and half of its pavements to forms that reflect more sunlight and absorb less heat could save up to 12 times what they cost to install and maintain, and reduce air temperatures by about 0.8 degrees.