Raising the Earth’s Albedo to Combat Warming?

By David L. Brown

Energy Secretary Steven Chu has stated that if we were to paint all flat roofs white it would reflect solar rays back into space and help reduce global warming. Well, maybe. Let’s take a look at what might be called the “albedo” solution.

The term “albedo” refers to the reflectivity of an object. It is most often used in astronomy to denote  the percentage of the Sun’s light that is normally reflected by a particular planet or other object. For example, the Moon reflects a paltry 12 percent on average, yielding an albedo index of 0.12. Venus, the brightest planet, reflects 65 percent for an albedo of 0.65. The Earth has an albedo of 0.37. These figures are averages for the entire surface of each object, so reflectivity could vary widely from place to place. For example on the Earth solar rays will strike bright white clouds in some locations and dark volcanic rock in others.

Albedo already plays an important role in the Earth’s ability to maintain temperature levels. Snow and ice in the Arctic and Antarctic reflect a lot of heat back into space. A serious concern about the ongoing loss of Arctic Ocean sea ice is the fact that dark open water will absorb a lot of heat that would previously have reflected off of the white snow and ice. Summer ice coverage has been shrinking, causing the Arctic to warm faster than any other region on the planet. This is called a feedback effect, since the more ice melts, the warmer the area will become, causing even more melting and so on.

Sec. Chu’s proposal to paint rooftops white is presumed to cool the Earth by raising the average albedo of the planet. He also noted that roads and sidewalks should also be made “lighter colored” to enhance the effect.

Dr. Chu is a Nobel Prize winning physicist and his ideas should not be discarded out of hand. Not surprisingly, FoxNews.com contributor Steven Milloy, known for his commentary on so-called “Junk Science” (www.junkscience.com) does exactly that. “It’s past simplistic — it’s ridiculous,” FoxNews.com quotes the avowed climate-change skeptic in this article. “Imagine the glare on roads, in urban areas, imagine the UV radiation bouncing around. Snow blindness would be replaced by road blindness.”


Who is Steven Milloy and should we pay attention to him? Well I won’t go into detail, but according to Wikipedia he is a self-described Libertarian who has received financial support from oil and tobacco companies, among others. It’s alleged that Philip Morris paid him more than $100,000 during a period in which he was branding the threat of second hand smoke as “junk science.” He has bachelor’s and master’s degrees in the fields of biology but his most advanced degrees are in law. In other words, he is a lawyer, not a scientist. In an editorial in Chemical and Engineering News, editor-in-Chief Rudy Baum called Milloy’s junkscience.com website “the best known” example of “a right wing effort in the U.S. to discredit widely accepted science, technology and medicine.” He went on to label Milloy “a tireless antiscience polemicist” who applies the term “junk science” to “anything that doesn’t match his right-wing concept of reality.”

As reported by FoxNews.com, Milloy said “We need sunlight to make vitamin D. Plants need it to make photosynthesis.”

That statement is a non sequitur par excellence. The idea behind it seems to be that if sunlight is reflected back from the Earth, it will reduce the amount of vitamin D or plant photosynthesis. That raises the question of how much vitamin D is produced by rooftops or roadways, and how much plant growth takes place there. I suspect, not much on either count. Milloy uses the words “simplistic” and “ridiculous” to describe Dr. Chu’s idea, but they could apply far more aptly to his own statements.

Countering Milloy’s rants, the Fox report quotes Dr. Gordon Bonan, a climate scientist at the National Center for Atmospheric Research in Boulder, CO, who “says there’s a kernel of truth in the science behind Chu’s idea.”

“That’s been a pretty standard idea for many years now,” says Bonan. “It’s related to the idea of an urban heat island — that a big city will generate a large amount of heat. In urban planning and urban design, the idea is that painting roofs white will absorb less solar radiation and keep the city cooler.

“In terms of roads, that does work,” he continued. “You can test it yourself by walking barefoot on a hot summer day. The asphalt is going to be much hotter than the concrete and the white lines painted on top of the asphalt.”

As far as Milloy’s objections about making roads and sidewalks a “lighter color,” it should be noted that like so many things it’s relative. Blacktop is black, but concrete is medium gray. True to form, Milloy assumes the extreme and speaks of road glare and “road blindness.” Perhaps the extreme isn’t what Chu had in mind, but it needs to be pointed out that the lower the albedo the smaller the benefit. On the other hand, top-dressing asphalt roads with chipped limestone could make a tiny difference and I suspect that a case could be made that lighter colored roads would be safer at night..

Leaving Milloy and his industry-supported rants aside, let’s look at the albedo solution from some other points of view. First, one must ask how much it would cost to paint every rooftop white—not only in terms of money, but also in terms of environmental impact. Paint is made from organic chemicals, and that means oil. It must be produced in an industrial process, packaged in some way, transported to the place of application, and applied through the use of some form of energy. All those things could contribute to global warming, a counter-effect to the desired outcome. Lime whitewash might be a more eco-friendly choice than paint, but needs to be refreshed every year or so.

There are other factors that perhaps Dr. Chu has considered and that might raise questions about the concept. For example, just because sunlight is reflected back from the Earth doesn’t mean that its heat passes completely away from the planet. In fact, it only gives it a second shot at warming the atmosphere as it travels back upward. This is a complex process and increasing the surface albedo might have far less impact than one might hope.

And just how much of the Earth’s area is covered with flat roofs ready to be painted white? A really small percentage, I’d hazard, especially compared with the vast areas of the Arctic and Antarctic ice sheets. The ultimate effect on the Earth’s albedo would be small at best and perhaps infinitesimal.

Some scientists speak or write of vast environmental engineering projects to offset global warming. Albedo often figures in such plans, ideas such as seeding clouds, spreading reflective materials on the surface, or even launching giant sun shades into space to reflect light away before it can reach the planet. The idea Dr. Chu proposed is something along those lines, although on a somewhat more modest scale.

One idea that makes sense is to pick up on that photosynthesis concern raised by Milloy. Why not turn rooftops into gardens, boosting the capability of the Earth to control its CO² content through greater vegetative growth. That would convert the solar rays into clean oxygen instead of reflecting them back into space, and the plant growth would absorb CO² from the atmosphere. Vegetative growth would also help clean the air of urban pollutants, provide a new source of food, and make it easier to keep buildings cool in summer by absorbing heat that would otherwise sink into the buildings themselves. To me, that seems to be a far more environmentally sound strategy.

Arguing conversely, why not paint buildings in darker colors, even matte black, in order to absorb more heat? That wouldn’t necessarily be bad if the heat were put to some useful purpose such as heating water or the buildings themselves. Layers of glass above a dark absorbing surface could capture even more of the heat and allow it to be channeled to where it is needed, or into underground heat sinks that could be drawn upon for warmth during cold seasons. Imagine brine tanks buried deep underground. Rooftops could even be converted into greenhouses to provide food year around in many temperate regions. The benefit? It would help replace the use of fossil fuels and the greenhouse gas they emit.

According to the news report, Dr. Chu claimed that his albedo scheme could have the same effect on global warming as removing all the automobiles in the world for eleven years, equal to removing 44 billion tons of CO² emissions. Well, maybe, but that doesn’t sound too scientifically rigorous. Eleven years compared to what? And what would be the economic and environmental cost of converting the roof and road surfaces to high-albedo reflectors of sunlight? What would be the cost-benefit ratio of such a plan?

I suggest we shouldn’t take Dr. Chu’s statement too seriously. Rather than being presented as “the answer,” we should view it more as a “what if…” thought experiment about one small factor that could contribute to cooling the Earth. The issues of global warming and climate change are extremely complex, and the solutions must be equally so. We need to look at every possible action that could contribute to a healthier planet, and every little bit will help.

I’ll leave you with my own outrageous (and tongue-in-cheek) proposal for a way to reduce global warming. My model is based on the effect of the eruption of Mount Pinatubo back in 1991. That event injected millions of tons of particulate matter into the atmosphere, and for more than a year we enjoyed spectacular sunsets—and cooler temperatures. The dust in the air blocked solar rays. (Note that this once again involved albedo.)

My “modest proposal” is a simple one, and it will solve problems of waste disposal as well as helping curb global warming. It would require little investment and could be put into effect quickly. It merely requires the passage of laws requiring everyone to burn their flammable trash in backyard barrels, thus adding smoke, dust and other Sun-blocking materials to the atmosphere. Viola! Lower temperatures. To carry this idea further, for the good of the planet smog control devices could be removed from automobiles, which could have the additional benefit of improving mileage and thus saving petroleum.

Yes, I know, this puts the desire to reduce global warming on a collision  course with every clean air mandate ever conceived. While possibly effective if implemented, it is totally unacceptable. I offer it only as an illustration of how difficult it is to solve any given environmental problem when the “green solutions” all too often create new problems or make old ones worse. Thus is the complex nature of our planet, and the magnitude of our challenges.

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