1 August 2006
Scientists say the appearance of rare clouds over Antarctica could be an indicator of global warming.
Dr Andrew Klekociuk from the Australian Antarctic Division says nacreous clouds are naturally-occurring, and indicate extremely cold temperatures in the stratosphere.
The stratosphere is between eight and 50 kilometres above the earth's surface, and gets colder as temperatures closer to earth get warmer.
Dr Klekociuk says as global warming increases, temperatures in the stratosphere should drop, and that has been reflected in data collected over the last 25 years.
"Over that time there has been a small decrease in temperature, and that change is actually occurring faster than the warming at the surface of the earth," he said.
"Now that's predicted by models, so it's quite possible the stratosphere is a good indicator of change happening lower down the atmosphere."
