Warming Creates More Night Shining Clouds

Dec. 10, 2007 -- Ice clouds at the edge of space are bigger, more prevalent and surprisingly variable, say researchers who believe the phenomenon may be partly due to global climate change.

The findings stem from observations by NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite, which studies noctilucent or "night-shining" clouds 50 miles above the polar regions.

The clouds are visible by night because they are so high above Earth that they are illuminated by sunlight while the ground below is in darkness. They appear during the summer months over both the north and south poles.

"These clouds are changing in ways that we don't understand," AIM principal investigator Jim Russell, with Virginia's Hampton University, said Monday at the opening of the American Geophysical Union Conference in San Francisco.

Researchers believe the clouds are more numerous and denser than expected due to changes in Earth's climate.

"The clouds are an exquisite thermometer," said Virginia Polytechnic Institute's Scott Bailey, deputy principal investigator for AIM.

Scientists have been keeping tabs on the clouds for about 27 years through a series of solar-watching satellites. AIM is the first mission devoted to studying the clouds exclusively.