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20th September 2008
Unlike other proposals to “geo-engineer” the climate, painting roofs and pavement white in tropical cities would have the same effect on global warming as cutting 44 billion tonnes of greenhouse-gas emissions
If all the cities in tropical and temperate climates required roofs and pavement to be tinted white, it would have the same effect on global warming as cutting 44 billion tonnes of greenhouse-gas emissions, the Global Climate Change Conference in Sacramento was told last week. That amount – more than the whole world pumps out in a year – would be worth about $1,100-billion (U.S.), based on the current price of carbon-offset credits.
The research, conducted by scientists at the Lawrence Berkeley National Laboratory in California, will be published in an upcoming issue of the journal Climatic Change.
Unlike other proposals to “geo-engineer” the climate, such as seeding oceans with iron to fertilize algae spawns (risking a collapse of the food chain) or spraying sulphur into the skies to block sunlight (but also precipitating acid rain), this idea is not controversial. And the concept is simple: White surfaces reflect more sunlight back to space than dark surfaces.
Moreover, buildings with white roofs are cooler, cutting the amount of energy used for air conditioning by about 20 per cent, as well as reducing air pollution from power plants and making cities less smoggy. The Berkeley scientists estimate that white roofs would result in energy savings of $1-billion (U.S.) a year in the United States alone.
California has mandated since 2005 that flat roofs be white and next year will require retrofitted and new sloped roofs to be “cool-coloured” (about half as reflective as pure white).
But white roofs and pavement made of a material more reflective than asphalt, such as concrete, will not solve our climatic problems on their own. Research leader Hashem Akbari notes that global greenhouse-gas emissions are still rising and a project of this scale would offset the estimated growth for only 11 years. “This plan basically buys us time to slow the rate of our emissions growth until we find permanent solutions to emit less and remove some of the carbon that we have dumped into the atmosphere.”
Published in The Green Report in The Globe and Mail
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