Normally rare noctilucent (“night shining”) clouds, which glow during the evening, are starting to move out of the polar regions to which they are normally confined, according to detailed pictures taken by a new NASA satellite.
Noctilucent clouds form 50 miles above the Earth’s surface, usually above the North and South pole during the summer months.
The "Aeronomy of Ice in the Mesosphere” (AIM) satellite imaged the noctilucent clouds as far south as Northern Europe on May 25. Not long after, they were seen in the sky by people living in that region.
The unusually southern appearance of these clouds is a clear sign that part of our atmosphere is changing, but scientists do not currently know how, why or what this means. The movement of the clouds suggests a global climate change in the lower atmosphere.
LiveScience June 28, 2007