Wired.com-6/13/13, Joe Hanson
Just after summer sunsets in northern latitudes, shimmering, wispy clouds appear in the twilight sky. This year, these noctilucent clouds have appeared earlier and farther south than ever before.
Noctilucent clouds exist higher in Earth’s atmosphere than any other cloud type. First observed in 1885 following the eruption of Krakatoa, they were a sight reserved for Earth’s northernmost residents. In recent years, however, their intensity and frequency have increased, often at latitudes previously thought to be too far south for noctilucent clouds to form.
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