Urban "heat islands" seen doubling city costs for climate change


Crowded cities could be affected twice as badly as their surroundings by climate change because of the "urban heat island" effect that traps warmth. Most of these studies are qualitative, except for the costs of sea-level rise in cities.

The research team carried out a cost-benefit analysis of different local policies for combating the urban heat island, such as cool pavements - created to reflect more sunlight and absorb less heat - cool and green roofs and expanding vegetation in cities.

But because cities generate vastly more wealth than the countryside, the impact of global warming will be much more significant unless measures are taken such as greening cities and using surfaces that reflect away heat and light.

The urban heat island effect is caused largely because concrete, stone and road surfaces tend to absorb considerable amounts of energy from the sun.

For the worst-off city, 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. Cities, which contribute more carbon to climate change than anywhere else, will also get hit by rising temperatures most severely.

In other words, cities are our future, just like climate change.

"The accumulated total costs of the urban impacts of global and local climate change for all cities during this century could be about 2.6 times those without urban heat island effects".

The study found that changing a fifth of a city's roofs and half the pavements to "cool" versions could save to 12 times the cost of installation and maintenance, while reducing air temperatures by an average of 0.8 degrees.

Therefore the impact on cities - which has been neglected - is of huge importance.

He said that the United Kingdom needs to take a leaf out of the book of countries such as Greece Spain, where buildings are often whitewashed, keeping them cooler, while in the United Kingdom they tend to be dark, which makes towns and cities hotter.

He said while ensuring the nations of the world do their bit to reduce greenhouse gases is very hard, 'a lot of things that can be done to mitigate urban heat island effects is well within the remit of the typical mayor'. The study's authors - from the University of Sussex in the United Kingdom, Universidad Nacional Autónoma de México and Vrije University Amsterdam - said these factors will likely add another two degrees, on top of global warming estimates, to urban areas by 2050.

Professor Tol said his team had come to the conclusions by estimating the economic costs of climate change on 1,692 cities worldwide including United Kingdom cities such as London, Edinburgh, Birmingham, Cardiff.

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

"We show that city-level adaptation strategies to limit local warming have important economic net benefits for nearly all cities around the world".