Rare clouds 'could indicate global warming'

Like brushstrokes rippling across the sky, this iridescent cloud dazzles with the colours of the fading sun.



Photographed over Antarctica, the rare nacreous cloud is made up of millions of ice crystals which bend and scatter the sun's rays, creating a pastel rainbow.

Also known as mother of pearl clouds, these formations only occur high in the atmosphere, in some of the coldest temperatures on Earth.

But their ethereal beauty may conceal a dark secret - it is thought that chemical reactions on the surface of the clouds help deplete the ozone layer.