Connection To Climate Change
There is evidence that the relatively recent appearance of noctilucent clouds, and their gradual increase, may be linked to climate change.
Atmospheric scientist Gary Thomas of the Laboratory for Atmospheric and Space Physics at the University of Colorado has pointed out that the first sightings coincide with the Industrial Revolution and they have become more widespread and frequent throughout the twentieth century. The connection remains controversial however. Wilfried Schröder was the first to explain noctilucent clouds as "indicators" for atmospheric processes (Gerlands Beiträge zur Geophysik, 1971, Meteorologische Rundschau 1968–1970).
Climate models predict that increased greenhouse gas emissions cause a cooling of the mesosphere, which would lead to more frequent and widespread occurrences of noctilucent clouds. A competing theory is that larger methane emissions from intensive farming activities produce more water vapour in the upper atmosphere. Methane concentrations have more than doubled in the past 100 years.
Tromp et al. suggest that a transition to a hydrogen economy could increase the number of noctilucent clouds through increased emissions of free hydrogen.
Read more about this topic: Noctilucent Cloud
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