Noctilucent clouds, silvery blue wisps that float high in our atmosphere, are a rare phenomenon – but rising greenhouse gas emissions mean we are seeing more and more of them
15 July 2020
THESE ghostly clouds add an ethereal edge to Knowlton church, a 12th-century ruin in Dorset, UK. Taken in the early hours by astrophotographer Ollie Taylor, the shot features silvery blue wisps known as noctilucent or night shining clouds. This rare phenomenon is only visible during twilight and is typically seen between May and August in the northern hemisphere and November and February in the southern hemisphere.
When the lower parts of the atmosphere heat up in the warmer months, air is pushed upwards to a colder layer of the atmosphere called the mesosphere. The water vapour in this air first condenses and then freezes into ice crystals around fine particles of dust that are thought to come from meteors. Volcanic dust and pollutants from the lower atmosphere may also play a role in the clouds’ formation.
Floating up to 85 kilometres above us, noctilucent clouds are the highest clouds in the atmosphere. Taylor used space weather updates, webcam observations and help from social media to track these unique and other-worldly streaks, which he says are the best he has seen in this region of England.
Sightings of noctilucent clouds have become more common in recent years, in line with the increase in greenhouse gas emissions, particularly of methane. As more methane enters the atmosphere, more of it is converted to water vapour that can then fuel the formation of these clouds.
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