The Park Service says that more than 90 percent of the time, scenic vistas in all of the parks are affected by man-made pollution.
Aidrin was nearly free of man-made pollution.
The salt crystals further contribute to the black effect that man-made pollution has on these buildings.
"This doesn't look like any man-made pollution I've ever seen."
They had their eyes opened to the man-made pollution that was fouling the oceans thousands of miles from land.
While specialists have learned a great deal about man-made pollution, they still know little of the atmospheric role of natural ecosystems.
"Almost all the time, we can pick up man-made pollution, sulfate pollution, on our monitors."
Natural sources like volcanoes, forest fires and lightning strikes also add to the man-made pollution.
Taken together, they represent the most forceful link yet made by respected institutions between man-made atmospheric pollution and global warming.
Algae blooms and sewage, which are indirectly created by man-made pollution, are visible, and have been photographed, from space.