Noctilucent clouds over Omaha on July 14.
Glowing clouds previously seen almost exclusively in Earth’s polar regions have appeared in the skies over the United States and Europe during the past several days.
Sky watchers in Omaha, Paris and Seattle plus several other locations have photographed what scientists call noctilucent ~ or ”night shining” ~ clouds. Formed by ice literally at the boundary where the earth’s atmosphere meets space 50 miles up, they shine because they remain lit by the sun even after the sun is below the horizon. According to Wired magazine:
The clouds might be beautiful, but they could portend global changes caused by global warming. Noctilucent clouds are a fundamentally new phenomenon in the temperate mid-latitude sky, and it’s not clear why they’ve migrated down from the poles. Or why, over the last 25 years, more of them are appearing in the polar regions, too, and shining more brightly.
“That’s a real concern and question,” said James Russell, an atmospheric scientist at Hampton University and the principal investigator of an ongoing NASA satellite mission to study the clouds. “Why are they getting more numerous? Why are they getting brighter? Why are they appearing at lower latitudes?”
Nobody knows for sure, but most of the answers seem to point to human-caused global atmospheric change.
Click here for the complete Wired Science article.