Professor Steven Chu: paint the world white to fight global warming

The Times
May 27, 2009

Mark Henderson, Science Editor

As a weapon against global warming, it sounds so simple and low-tech that it could not possibly work. But the idea of using millions of buckets of whitewash to avert climate catastrophe has won the backing of one of the world’s most influential scientists.
Steven Chu, the Nobel prize-winning physicist appointed by President Obama as Energy Secretary, wants to paint the world white. A global initiative to change the colour of roofs, roads and pavements so that they reflect more sunlight and heat could play a big part in containing global warming, he said yesterday.
Speaking at the opening of the St James’s Palace Nobel Laureate Symposium, for which The Times is media partner, Professor Chu said that this approach could have a vast impact. By lightening paved surfaces and roofs to the colour of cement, it would be possible to cut carbon emissions by as much as taking all the world’s cars off the roads for 11 years, he said.
Building regulations should insist that all flat roofs were painted white, and visible tilted roofs could be painted with “cool-coloured” paints that looked normal, but which absorbed much less heat than conventional dark surfaces. Roads could be lightened to a concrete colour so they would not dazzle drivers in bright sunlight. “I think with flat-type roofs you can’t even see, yes, I think you should regulate,” Professor Chu said.
Pale surfaces reflect up to 80 per cent of the sunlight that falls on them, compared with about 20 per cent for dark ones, which is why roofs and walls in hot countries are often whitewashed. An increase in pale surfaces would help to contain climate change both by reflecting more solar radiation into space and by reducing the amount of energy needed to keep buildings cool by air-conditioning.
Professor Chu said that his thinking had been influenced by Art Rosenfeld, a member of the California Energy Commission, who drove through tough new building rules in the state. Since 2005 California has required all flat roofs on commercial buildings to be white; the measure is being expanded to require cool colours on all residential and pitched roofs.
Dr Rosenfeld is also a physicist at the Lawrence Berkeley National Laboratory in California, of which Professor Chu was director. Last year Dr Rosenfeld and two colleagues from the laboratory, Hashem Akbari and Surabi Menon, calculated that changing surface colours in 100 of the world’s largest cities could save the equivalent of 44 billion tonnes of carbon dioxide — about as much as global carbon emissions are expected to rise by over the next decade.
Professor Chu said: “There’s a friend of mine, a colleague of mine, Art Rosenfeld, who’s pushing very hard for a geo-engineering we all believe will be completely benign, and that’s when you have a flat-top roof building, make it white.
“Now, you smile, but he’s done a calculation, and if you take all the buildings and make their roofs white and if you make the pavement more of a concrete type of colour rather than a black type of colour, and you do this uniformly . . . it’s the equivalent of reducing the carbon emissions due to all the cars on the road for 11 years.”
The US needed to increase its investment in clean energy research, he said, citing high-tech industries that spent 10 to 20 per cent of their income on research. The US was spending $1 trillion on generating electricity, but “nothing like” the $100 billion to $200 billion on research that would meet that standard, he said.
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