Murphy says you could look out the window of the airplane and see the air colored brown as you were flying, even though you're hundreds or thousands of miles from the nearest big city. He talks about the sources of this haze.
A 12-year veteran of environmental journalism, Dan Kulpinski is a frequent contributor to EarthSky. He also publishes the GreenListDC.org site and the GreenListDC Blog. Before joining EarthSky, he was a programming director at AOL and wrote the AOL Down to Earth blog.