14 DAY TRIAL // Dark-colored, rocky, bare and dry areas on Earth are the places where the highest temperatures are recorded. Though one may be tempted to think that deserts are the hottest places around, this is simply not the case. Now, experts suggest that we should make cities less dark-colored.
When seen from above, our largest cities are oftentimes a patchwork of colors, most often black or gray. These nuances interact with sunlight in a manner that is very detrimental to our well-being.
For example, black street tarmac and dark rooftops accumulate a lot of heat during the day, as they are bathed in sunlight. They release this energy at night. When combined with the fact that cities are highly polluted, the results are devastating.
Large amounts of carbon dioxide (CO2) are emitted in the air, and they create a greenhouse effect, trapping heat at the surface. Cities therefore get extremely warm, a fact that contributes to the increased incidence of skin cancers and respiratory disorders doctors have begun warning about.
The image to the left shows a section of Queens, New York. It was collected on September 15, 2010, using the DigitalGlobe Worldview-2 satellite, and shows a wide variety of colors, including a lot of black and gray.
Official statistics from the US Environmental Protection Agency (EPA) indicate that highly urbanized areas can experience temperatures about 6° Celsius (10° Fahrenheit) warmer than surrounding areas. This is called the “heat island effect.”
“I see surface temperatures in the city that routinely exceed what you might find in the desert,” explains Stuart Gaffin, who is the Lamont associate research professor at the Columbia University Center for Climate Systems Research (CCSR).
“Cities have been progressively darkening the landscape for hundreds of years. City roofs are traditionally black because asphalt and tar are waterproof, tough, ductile and were easiest to apply to complex rooftop geometries,” he adds.
“But from a climate and urban heat island standpoint, it makes a lot of sense to install bright, white roofs. That's why we say, ‘Bright is the new black’,” the investigator goes on to say. By adding more white and green to rooftops, it may be possible to decrease the high temperatures plaguing large cities, NASA reports.