The World Bank clearly believes the idea – the brainchild of 55-year-old Peruvian inventor, Eduardo Gold – has merit as it was one of the 26 winners from around 1,700 submissions in the “100 Ideas to Save the Planet” competition at the end of 2009.
From the same article (2010):
Although he is yet to receive the $200,000 (£135,000) awarded by the World Bank, his pilot project is already underway on the Chalon Sombrero peak, 4,756 metres above sea level, in an area some 100km west of the regional capital of Ayacucho.
From an article at Adventure Journal (2011):
The World Bank ponied up the $41 billion to cover the 1,200 square miles.
Gold says that when he compared, the temperature of the white rock vs. the black rock he saw a difference averaging 10-12 degrees Celsius, which is pretty dramatic. He also says this has led to the formation of ice, and that that has led to more abundant water in the villages below. If you’re waiting for harder science, well you should. Gold and his team have only painted four acres or so of one mountain, which makes it hard to believe that whatever effect the cooling has had, it’s amounted to any significant localized precip. And even if he’d painted 100 times that area, it would still be very difficult to prove much beyond a steady stream of data showing what we already know: white surfaces are cooler than dark ones.
I tried to find an update to see how this worked out. Haven’t found anything yet.