18 July 2020 | New Scientist | 27Silver linings
Photographer Ollie Taylor
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. ❚
Gege Li