A Sky Less Blue

Astronomers have been complaining for a long time about the dimming of the night sky.  Light pollution from increasingly bright urban centres has been diminishing the ability of ground based telescopes to view the sky.  During the great blackout on August 14th, 2003, when most of the eastern seaboard in Canada and the United States went dark, the first thing most people noticed were the stars.

I'm not sure it occurred to anyone that something similar might be happening to the daytime sky, but apparently so.  Wang and colleagues have just published a new study in the journal Science showing that air pollution is scattering light particles making the clear daytime blue sky, less blue.

I recall a whimsical reference in Douglas Adam's "Hitch-hikers Guide to the Galaxy," to a super-intelligent shade of the colour blue.  Our blue skies no longer seem so intelligent.

Shown above is a simulation of the affect achieved by combining the sky of San Francisco with pollution levels evident in southeast Asia.  

Reference: Wang K, and others. 2009. Clear sky visibility has decreased over lanPublish Postd globally from 1973-2007. Science 323 (5921)

Photo Credit: Brandon Keim (Wired Science) with direction from K Wang.