For hundreds of years, architects have recognized the important role that white roofs play in reflecting sunlight and keeping the homes below cool. Around the Mediterranean Sea, cities built on hill slopes are all painted white, to offset the high temperatures registered there annually. New reports confirm that buildings with white rooftops and streets paved with concrete instead of asphalt could offset huge quantities of carbon emissions worldwide.
 

Scientists attending the Climate Change Research Conference in California argue that, if 100 of the world's largest cities were to change the color of all building roofs to white, some 44 metric gigatons of carbon would be removed from the atmosphere. That is to say, we're talking about 44 billion metric tons of gas that would otherwise rise back into the atmosphere and contribute to global warming and climate change.

 
It's common knowledge that darker colors absorb more light and heat than lighter ones. People wearing black t-shirts on the street feel the temperature as being higher than those wearing white shirts, for example. The same principle applies to buildings as well. Brown or black roofs attract sunlight and heat, thus increasing the costs of operating air conditioners, which, in turn, place an ever increasing strain on the power grid. Larger demands mean that electric plants need to work overtime and burn more fossil fuels, which are the main source of the dangerous carbon emissions.

 
On one hand, the cities get warmer because of the color of their rooftops and the fact that their streets are paved with dark asphalt – a cheap material coming from the petroleum industry – that further generates heat, and on the other hand, the increased demand of electricity needed to cool down the cities generates more carbon. That's a vicious circle that can only be broken if firm action is taken to alter the appearance of the cities. A change like that has the capacity to offset a huge portion of all greenhouse gases emitted in the world today.