you know what to do!

New Scientist has a little piece on the subject: “Would it be possible to reduce the impact of the greenhouse effect by painting roofs of buildings white to reflect sunlight in the same way the polar icecaps do?”

To answer that question, the the Earth Institute at Columbia University (New York) has undertaken the Global Rural Urban Mapping Project (GRUMP).

Its results show that roughly 3 per cent of the Earth’s land surface is covered with buildings. The Earth has an albedo of 0.29, meaning that it reflects 29 per cent of the sunlight that falls upon it. With an albedo of 0.1, towns absorb more sunlight than the global average.

Painting all roofs white could nudge the Earth’s albedo from 0.29 towards 0.30.

According to a very simple “zero-dimensional” model of the Earth, this would lead to a drop in global temperature of up to 1 °C, almost exactly cancelling out the global warming that has taken place since the start of the industrial revolution.

A zero-dimensional model, however, excludes the atmosphere and, crucially, the role of clouds. But! It would be interesting to see if more sophisticated models predict a similar magnitude of cooling.

So next time you replace the tiles on your roof or buy a new house, you know what to do (if you can’t/won’t get solar panels, white tiles or a green roof, at least try to get a light color).

Tree Hugger, 16 Dec 2005