This green idea has been headlined a few times recently. The articles have declared that painting roofs white would save more than the equivalent space put into expensive solar panels. It is a good idea for a green and energy-efficient world – at least in the hotter and sunnier climates. In the US the demographics have changed, slipped toward the Sun Belt which makes the idea far more appropriate than it would have been before the Rust Belt rusted.

It is not such a radical idea – the painting of roofs white and reflective rather than the usual New England-like fake-slate or tar-black. The difference now is that photo-voltaic panels and hoped-for solar technologies are becoming available and therefore tempting as an active, visible, high-tech solution to a world crisis. Green is now the color of goodness and virtue; businesses and institutions are itching as if they had poison ivy to climb up the green stalks toward global responsibility.

One such report in Business Week sagely noted that the 21st century world is often dominated by the notions that “complex problems require complex solutions.” But they point out that the environmentally correct solution is probably that white paint is often cheaper and better than the expensive and glittering solution. K.I.S.S. — Keep It Simple Stupid – is the hard lesson of a high tech world. An iPhone might be, should be, probably will be fun, useful and the summit of cool. But when its battery is down and the power is out after the storm to recharge it; that $10 analog phone will come out of the closet because it is simple enough to work.

General Roof Management's web site touts its “Cool Roofs” program for an example. It is being written into code requirements in California — a place where “green” is a charged word-- Georgia and Chicago. Their Cool Roofs are white or light-colored roof surfaces which, they write, have surface temperatures 30-90 degrees (F) cooler than more conventional roofing. This lowers the costs of cooling the building by 20-50%.

Plant Services.com writes that a typical flat, tar-black roof can get to 170 F in summer. Further they point out that these hot roofs contribute to the “heat island effect” which is said to be connected to increased carbon dioxide levels in urban areas. The heat build-up also requires extra fossil-fuel use to generate power for the additional cooling loads.

The relative reflectivity of the Earth itself is of interest in the nature of cooling. A black earth somehow denuded of clouds, ice caps, glaciers, deserts would be a hot place indeed. The Business Week article compared a dark Earth to a black leather car interior on a hot day and the Earth with those light-colored features as a car with a beige leather interior. In the jargon of planetary scientists the “albedo” of the planet – its relative level of reflectivity – is 30%.

The new element affecting the albedo of Terra is the presence of greenhouse gases in the atmosphere which contain additional heat. The sun gives Earth 1350 constant watts of energy, of illumination. Some is absorbed, some reflected by the light-colored features. In the modern, industrial world an additional 2 watts per square meter is retained over the retained levels in the world before it became industrialized.