Mysterious, Glowing Clouds Over US Night Skies

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Mysterious, glowing clouds previously seen almost exclusively in Earth’s polar regions have appeared in the skies over the United States and Europe over the past several days.


Over the last 125 years, scientists have learned how the clouds form. At temperatures around minus 230 degrees Fahrenheit, dust blowing up from below or falling into the atmosphere from space provides a resting spot for water vapor to condense and freeze. Right now, during the northern hemisphere’s summer, the atmosphere is heating up and expanding. At the outside edge of the atmosphere, that actually means that it’s getting colder because it’s pushed farther out into space.

It’s not hard to see how a warming Earth could change those dynamics: as the globe heats up, the top of the atmosphere should get colder.

“The prevailing theory and most plausible explanation is that CO2 buildup, at 50 miles above the surface, would cause the temperature decrease,” Russell said. He cautioned, however, that temperature observations remain inconclusive.

The global changes that appear to be reshaping noctilucent cloud distribution could be much more complex, said Vincent Wickwar, an atmospheric scientist at Utah State University whose team was first to report a mid-latitude noctilucent cloud in 2002. Temperature does not explain their observations from around 42 degrees latitude.

“To get the noctilucent clouds you need temperatures that are about 20 degrees Kelvin colder than what we see on average up there,” Wickwar said. “We may have effects from CO2 or methane but it would only be a degree or a fraction of a degree.”

Instead, Wickwar’s explanation is that a vertical atmospheric wave discovered in their LIDAR data lowered the temperature in the region above their radar installation near Logan, Utah. But then you have to ask, he noted, “Where’d the wave come from?”

They don’t really have an answer yet. Other facilities around the world with similar LIDAR capacity haven’t reported similar waves. And the Rocky Mountains, near Wickwar’s lab, can cause atmospheric waves, which could be a special feature of his location.

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Other theories abound to explain the observed changes in the clouds. Human-caused increases in atmospheric methane, which oxidizes into carbon dioxide and water vapor, could be providing more water for ice in the stratosphere. Increases in the amount of cosmic or terrestrial dust in the stratosphere could also increase the number of brightly shining clouds.

Two years into Russell’s NASA project, more questions exist than firm answers. They will have at least three and a half more years, though, to gather good data on upper atmospheric dynamics.

The recent observations of noctilucent clouds at all kinds of latitudes provide an extra impetus to understand what is going on up there. Changes are occurring faster than scientists can understand their causes.

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