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History of airborne soot, America (Read 143 times)
lee
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History of airborne soot, America
Oct 12th, 2017 at 6:26pm
 
"Horned Larks are cute songbirds with white bellies and yellow chins—at least, now they are. One hundred years ago, at the height of urban smoke pollution in the United States, their pale feathers were stained dark gray by soot in the atmosphere.

A new paper in the Proceedings of the National Academy of Sciences shows that the discoloration of these birds in museum collections can be used to trace the amount of black carbon in the air over time and measure the effects of environmental policy on pollution.

“The soot on these birds’ feathers allowed us to trace the amount of black carbon in the air over time,” said study author Shane DuBay, a graduate student in the Committee on Evolutionary Biology at the University of Chicago and The Field Museum. “We found that the air at the turn of the century was even more polluted than scientists previously thought.” "

"“When you touch these birds, you get traces of soot on your hands. We’d wear white gloves while handling them, and the gloves would come away stained, like when you get ink on your fingertips reading a newspaper,” DuBay said, because the soot in the air clung to the birds like dust to a feather duster. “These birds were acting as air filters moving through the environment.”

Birds were also ideal candidates for the study because they molted and grew new sets of feathers every year, meaning that the soot on them had been accumulating only for the past year when they were collected. And there was an apparent trend: old birds were dirtier, and new birds were cleaner."

https://news.uchicago.edu/article/2017/10/10/soot-covered-birds-provide-clues-20...

So these birds show both global dimming, due to the soot, and global brightening due to the cleaner air.

Global dimming causes less heat to arrive at the earth's surface.
Global brightening the opposite.
Clean air causes warmer temperatures.
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