Urban heat island effect intensifies climate change costs for major cities

This century the total economic costs of climate change for major cities could be 2.6 times higher

Climate change caused by the 'urban heat island' effect may cost world's major cities twice as much as the rest of the planet, researchers warned.

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

This effect is expected to add a further two degrees to global warming estimates for the most populated cities by 2050, the study published in the journal Nature Climate Change revealed.

The findings, based on an analysis of 1,692 cities of the world, indicated the total economic costs of climate change for cities this century could be 2.6 times higher when heat island effects is taken into account than when they are not.

The losses could reach 10.9 per cent of GDP by the end of the century, compared with a global average of 5.6 per cent.

"Any hard-won victories over climate change on a global scale could be wiped out by the effects of uncontrolled urban heat islands," said Richard S.J. Tol, Professor at the University of Sussex.

Although cities cover only around one per cent of the Earth's surface, they produce about 80 per cent of Gross World Product, consume about 78 per cent of the world's energy and are home to over half of the world's population.

Cost-efficient local policies such as cool pavements designed to reflect more sunlight and absorb less heat. Cool and green roofs and expanding vegetation in cities could limit the high economic and health costs of rising urban temperatures and help combat the urban heat island.

Changing 20 per cent of a city's roofs and half of its pavements to 'cool' forms could save up to 12 times what they cost to install and maintain, and reduce air temperatures by about 0.8 degrees, the researchers said.