the sky isn’t falling – it’s shrinking!

Scientists have discovered yet another enigma about our planet: the thermosphere has undergone serious shrinkage. The thermosphere is the largest portion of the Earth’s atmosphere and is the next-to-last region before you reach the vacuum of outer space.

While we are coming out of one of the longer periods of low solar activity in a century, scientists have found that the thermosphere has shrunk some 28 percent. That’s the largest drop in recorded history, and they cannot explain why.
ars technica, 22 Jul 2012