You might think that this idea sounds a little crazy but I urge you to read on.   Here’s the idea:  Everyone paints the roof of their house white and the rate of global warming will be radically reduced!

Insane?  Well, this idea does have some sense and logic to it.  I recently discussed this with my friend Ken Caldeira at Stanford University.  Over some monstrously huge American sandwiches, our discussions eventually came round to the amazing impact that losing the reflectivity of Arctic summer ice would have on the rate of global warming.  A few back of the envelope calculations by Ken soon convinced the people around the lunch table that changing the reflectivity of an even 1% of the Earth’s surface could have a major impact on the amount of trapped radiation solar.  Flip side?  Essentially, losing the albedo of the Artic sea ice is like piling massive amounts of CO2 into the atmosphere.  

Back at Ken’s lab, discussions with Long Cao (one of Ken’s postdoctoral fellows) turned to whether or not one could influence this effect by manipulating the reflectivity of the earth through other means – What about doing a Christo? What about covering large areas with white chalk or mirrors?  What about inventing a highly reflective plant that would spread out across arid areas and change the reflectivity of desert regions?   Interestingly, the quick search of the literature revealed that this latter idea is being actively explored by scientists:

Andy Ridgwell and colleagues at the University of Bristol in England have another idea, one they call bio-geoengineering. Rather than developing infrastructure to help cool the planet, they propose using an existing one: agriculture. Their calculations, published in Current Biology, suggest that by planting crop varieties that reflect more sunlight, summertime cooling of about 2 degrees Fahrenheit could be obtained across central North America and a wide band of Europe and Asia. Plants reflect slightly different amounts of light depending on factors like how waxy the leaves are. Even differences in growth patterns between two varieties of a crop — the way leaves are arranged — can affect reflectivity.  (Read More)

Now, Steven Chu, the Nobel prize-winning physicist appointed by President Obama as Energy Secretary, has proposed that we seriously explore this idea.  Rather than use the rather challenging (from all aspects!) idea of engineering plants, Steven would like to whitewash the world – to initiate a global initiative to change the colour of roofs, roads and pavements so that they reflect more sun?

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. 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. (Read More)

Not a bad idea at all – and one that would be achievable in a short-period of time. It would work like this: basically, governments would institute the painting of the tops of roofs and buildings (traditionally black tar, slate, or grey colours) white, this would alter the albedo (surface reflectivity of the sun’s radiation), effectively reducing the amount of heat trapped by the Earth’s surface to offset projected increases from global warming.

As a weapon against global warming, this idea sounds so simple and low-tech that it just might work.  It could be used to reduce warming associated risks and buy some important time as we struggle to bring emissions down. As with all of these ideas, however, we must also be cautious not to use them as an excuse for not dealing with the problem of rising atmospheric CO2.  These measures will only offset part of the problem and certainly will be exceeded in time. And, clearly, reducing global temperature in this way will do nothing for problems like those assoociated with ocean acidification.