Rare clouds 'could indicate global warming'
By FIONA MACRAE, Daily Mail 19:38pm 1st August 2006
These wispy clouds could indicate the effects of global warming

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.
This spectacular picture was taken at sunset in East Antarctica. The
clouds' formation is dependent on a combination of extreme weather
conditions, including temperatures below minus 80c, and they are visible
only at sunrise and sunset.

This nacreous cloud was captured on film by scientists at the Mawson
research station, who estimate it had formed 12 miles above Earth, in
winds of 140mph and in temperatures as low as minus 83c.
Researcher Dr Andrew Klekociuk said clouds as spectacular as this are
very rare. "You have to be in the right part of the world in winter and
have the sun just below your horizon to see them," he added.

"Our expeditioners at Mawson are in one of those special parts of the
world."
Meteorologist Renae Baker captured the clouds on film as they lit up the
winter sky. She said: "Spectacular is an understatement. The clouds were
such a special and welcoming sight now that the sun has just started to
return near the end of winter. I am keeping my camera at the ready in
the hope of some more."
Dr Klekociuk, an atmospheric scientist, added: "These clouds are more
than just a curiosity.

They reveal extreme conditions in the atmosphere and promote chemical
changes that lead to the destruction of vital stratospheric ozone."

The clouds may also be an indicator of global warming. The build-up of
carbon dioxide in the atmosphere that traps heat on Earth, causing it to
heat up, also stops heat from reaching the stratosphere and causes it to
become cooler.

If global warming gets worse, these clouds could be a regular sight.