Nacreous clouds

Nacreous clouds over the NASA Radome, McMurdo Station, Antarctica. (Photo: Alan Light/flickr)

During the winter in far northern and southern climes — like Scandinavia, Iceland and Antarctica — the twilight sky occasionally offers a sight of deceptively staggering beauty. You may have seen clouds tinged with rainbow edges before, but nacreous clouds, known as polar stratospheric clouds, fill the heavens with vividly undulating iridescent colors that are singular in their beauty.

But while they may create a firmament worthy of magic and unicorns, they are actually wreaking havoc on our atmosphere.

Nacreous clouds form in the stratosphere, well above tropospheric clouds at 70,000 feet or above — twice as high as commercial planes fly — where the ozone layer resides. And unfortunately, these mother-of-pearl clouds are a major factor in the creation of ozone holes in the Arctic and Antarctic.

Usually it’s too dry in the stratosphere for clouds to form, but nacreous clouds and their mixture of supercooled water, ice crystals and nitric acid are different. And because of their unique composition, they become the perfect partner for chemical reactions from human-produced chlorofluorocarbons (CFCs), resulting in the release of chlorine gas, which breaks down ozone.

So although they may be gorgeous to look at, it’s safe to say that not all clouds have a silver lining. But since mankind has made a concentrated effort to reduce CFC emissions, eventually nacreous clouds will be a thing of the past. Until then, they will remain a thing of poignant yet tragic beauty.

Nacreous clouds

Nacreous clouds over Asker, Norway. (Photo: Wikimedia Commons)

Polar clouds

Photo: Florentin Moser/Wikimedia Commons

Nacreous clouds

Nacreous clouds over Gaellivare, Lapland, Sweden. (Photo: Bildagentur Zoonar GmbH/Shutterstock)

polar stratospheric clouds

Nacreous clouds over Asker, Norway. (Photo: Sondrekv/Wikimedia Commons)

Mother-of-pearl clouds

Nacreous clouds over "Roll Cage Mary," McMurdo Station, Antarctica. (Photo: Alan Light/flickr)

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Nacreous clouds illuminate the twilight sky
Polar stratospheric clouds are beautiful to look at, but does their destructive dark side spell doom?