Are noctilucent clouds a “Miner's Canary” for global change?

Noctilucent clouds (NLC) occur close to 83 km altitude during summer at polar, high, and mid‐latitudes. They are frequently visible to Earth‐bound observers, provided the observers are on the night side of Earth and the clouds are still illuminated by the Sun. Under these conditions, NLC can become a quite impressive sight. NLC owe their existence to the extremely low temperatures (well below 150 K) which prevail during summer over a wide latitude band in the 82‐ to 90‐km altitude region. For a major review of NLC science, the reader is referred to Gadsden and Schröder [1989].