Once it was thought that HFCs were better than CFCs till HFCs came up with their own plate of woes! White roofs are the simplest solutions in hot cities, and one would have thought that reflecting back sunlight would reduce global warming. But no!
Mark Jacobson’s (of MIT) computer modeling concluded that white roofs did indeed cool urban surfaces. However, they caused a net global warming, largely because they reduced cloudiness slightly by increasing the stability of the air, thereby reducing the vertical transport of moisture and energy to clouds. In Jacobson’s modeling, the reduction in cloudiness allowed more sunlight to reach the surface.
The increased sunlight reflected back into the atmosphere by white roofs in turn increased absorption of light by dark pollutants such as black carbon, which further increased heating of the atmosphere!
There is no solution to all our problems, it seems. When one is solved, another pops.
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