Thousands of lives lost each year in heatwaves could be prevented by painting roofs white, new research suggests.
Cities can heat up by an extra 9°C (16°F) compared to surrounding areas - an effect called the 'urban heat island'.
But painting roofs in colours that reflect heat back into space can keep buildings significantly cooler, research has found.
Around half of deaths during heatwaves - mainly the elderly - are thought to be caused by the extra heat in cities.
Experts calculate how many people die during heatwaves, compared to how many would die normally.
For example, the 2003 heatwave is thought to have caused the deaths of 2,000 people in England and in July 2009 a four-day spell of hot weather killed 300 people.
The Oxford University study said the 'heat island' effect is caused partly by a lack of moisture and vegetation in cities compared with rural landscapes, and because urban building materials store up heat.
The scientists calculated how much temperatures would drop in the city of Birmingham, simulating heat levels seen in the hot summers of 2003 and 2006.
The study, published in Environment International, suggested that implementing cool roofs across the city can reduce peak daytime local temperatures by up to 3c during a heatwave.
To achieve this reduction would require around half of the commercial and industrial buildings in the city to paint their roofs.
This reduction in temperature could potentially offset around 25 per cent of the heat-related mortality associated with the urban heat island during a heatwave.
Applied worldwide it would lead to reductions of thousands of deaths, the research suggests.
The urban heat island effect is most pronounced at night time, because urban materials slowly release their stored heat overnight, however, the biggest benefits of cool roofs were seen to be during the hottest part of the day where sunlight was reflected away.
Co-author Dr Clare Heaviside, of the University of Oxford's Environmental Change Institute comments: 'Climate change and increasing urbanisation mean that future populations are likely to be at increased risk of overheating in cities, although building and city scale interventions have the potential to reduce this risk.
'Modelling studies like this one can help to determine the most effective methods to implement in order to reduce health risks in our cities in the future.'
This article has been adapted from its original source.
