Over the last couple of days, nacreous clouds have been busting out all over. The BBC among other places has galleries of images of the mother-of-pearl effect atmospherical vapours.

A colleague into cloudspotting forwarded a link to this Guardian article from 10 years ago, ‘The cloud with a dangerous secret’. Cloudspert Gavin Pretor-Pinney (author of the well-worth-having Cloudspotters’ Guide) considered the portents to be gleaned in these airy swooshes of iridescent loveliness as ‘worrying’:

Besides causing beautiful opalescent colours, nacreous clouds’ tiny ice crystals also act to encourage chemical reactions between ozone and the chlorine and bromine that we have introduced into the atmosphere by our use of substances such as chlorofluorocarbons (CFCs) in aerosols and fridge mechanisms. Without the presence of stratospheric clouds, reactions leading to the destruction of the ozone layer are negligible. The nacreous cloud’s ice particles behave as nuclei on to which the ozone breakdown can take place.

Oh dear. Took the edge right off the delicious aerial show, the shimmering suddenly most melancholy. The ozone layer was at its thinnest in 2006, although 10 years on it is apparently on the mend, according to this Independent article from 2014:‘Ozone layer is healing…’. Of course, reading the rest of the headline and article, it seems a particularly small crumb of comfort to not be getting as much skin cancer from UV rays as we slowly continue to cook like frogs in a pot.

All of which context I will probably not mention to our three year old if we are watching the pretty sky again tomorrow morning.

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