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Fighting Global Warming with Pavement Fighting Global Warming with Pavement
The Planet

Fighting Global Warming with Pavement

by Seth Shostak

July 16, 2009

A new color scheme for our roads and highways could take some of the heat off Earth's climate.

You may not have given it much thought, but your boistrous lifestyle runs at about 10 kilowatts, day and night. Thirteen horsepower, if you prefer equine units.That's the average power consumed by each man, woman, and child in the United States-the energy burden of everything you do and use-from heating up dinner and cooling your apartment, to dashing out to the convenience store in your candy red Bugatti. And while some of that energy is used for illumination, the overwhelming majority degrades to heat.Consider: At the end of an all-day drive, what happened to the chemical energy in the tank of gas you bought before breakfast? It's gone into heating up the engine, the tires, the brakes, and the air pushed out of the way by the hood ornament. Virtually all of the calories in that refined natural resource you bought for $3 a gallon end up warming the atmosphere.Our energy burn is impressive. The residents of a burg the size of Baltimore pump out 5 billion watts of heat just to enjoy life, or about 20 times the total sunlight beating down on the city. World-wide, our species is toasting Earth's atmosphere at the rate of 10 trillion watts. That's a lot of BTU pleasure.OK, the heat's on. We know that, and we've all heard the standard approaches to dealing with our profligate ways.But here's my odd idea of something we could do that isn't so standard: implement a pavement plan to mitigate atmospheric heating.It goes like this: We've been busy for nearly a century covering the civilized world with highways and byways. If you laid all the hard-surface roads in the United States end to end, they'd stretch for 2.5 million miles. That pavement covers a lot of ground, quite literally, and amounts to nearly one percent of our country's total acreage (for comparison, the national parks total four percent).Now you may have noticed that many of those motorways are pretty dark. Indeed, the reflectance of most roads is roughly 20 percent; that is, they return only about one-fifth of the sunlight hitting them. But the stripes that skip down their centerlines have a reflectance of about 50 percent, as measured with my camera's light meter. That's why you can see these pavement markings: they're twice as bright as the asphalt.So here's my idea: we just invert this situation, and construct white pavement with black stripes.Not only will this improve your ability to follow the road at night (while simultaneously lining the pockets of construction workers nationwide), it will more than double the amount of sunlight reflected by roads-and thereby reduce the amount of atmospheric heating.How much? Well, my back-of-the-napkin calculation suggests inverting the pavement color scheme would bounce an additional 5 trillion watts skyward.Is that significant? You bet your Wellingtons. NASA has recently estimated that the Greenland ice sheet is currently melting at the alarming rate of 50 cubic miles of ice per year. Invoke a bit of high school physics, and you can figure that 2 trillion watts of continuous heating will melt that volume of ice. But merely by changing the color of pavement, we can reduce the amount of atmospheric heating by roughly three times that amount.In other words, we could save the Greenland ice cap with road crews. Sounds pretty cool to me, and this project is shovel-ready.Now … want to hear about my mirror roof tiles?Guest blogger Seth Shostak is a Senior Astronomer at the SETI Institute. He is the author of Confessions of an Alien Hunter: A Scientist's Search for Extraterrestrial Intelligence, and hosts SETI's radio show Are We Alone?
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Fighting Global Warming with Pavement