Imagine a world where the rooftops and pavements of every urban area are resurfaced to increase the reflection of the Sun's light rays. Well, this is exactly what a group of Canadian researchers have simulated in an attempt to measure the potential effects against global warming. In a study published April 13, in IOP Publishing's journal Environmental Research Letters, researchers from Concordia University created this scenario¹ to see what effect a global increase in surface reflectance（反射比） would have on global temperature and our own carbon dioxide (CO2) emissions².

They estimate that increasing the reflectance -- commonly known as albedo（反射率） -- of every urban area by 0.1 will give a CO2 offset³ between 130 and 150 billion tonnes. This is equivalent to taking every car in the world off the road for 50 years, assuming a single car gives off around 4 tonnes of carbon dioxide a year.

This could also provide huge financial gains: CO2 is currently traded at $25 a tonne meaning savings⁴ could be in the range of $3300 and $3800 billion dollars.

Albedo is measured on a scale ranging from 0 for a non-reflecting, perfectly⁵ black surface to 1 for a perfectly white surface. The albedo of all roofs can be increased, on average, by 0.25 and all paved surfaces can be increased by about 0.15. The researchers believe this will increase a city's overall albedo by about 0.10.

Researchers have long proposed that changing the albedo of a surface could be an effective way of reducing CO2 emissions. A change could effectively cool buildings that would usually retain heat and therefore reduce the use of air-conditioning systems; it could also improve outdoor air quality and offset the warming that the world is currently experiencing.