There the water freezes into noctilucent clouds. Methane has doubled in the last century from agricultural activities, mainly rice paddies and cattle passing gas. You take away life and there's no methane in the atmosphere at all. More carbon dioxide may also fuel clouds by cooling the upper atmosphere. Though increasing carbon dioxide levels warms the lower atmosphere, it cools the upper atmosphere by releasing heat to space.
More carbon dioxide means more cooling.
In 1994, Thomas predicted the clouds would get brighter and extend farther south in the next 100 years, but he didn't expect to see them so soon. A sighting even farther south near the Colorado-New Mexico border was reported last Friday but was not confirmed with photos or Lidar. Taylor says photographs are key if you think you've seen a noctilucent cloud. Most of the noctilucent cloud studies have been done by amateurs. From those measurements, scientists have been able to tell these clouds are increasing.