Falling skies? Clouds got lower in past decade, say scientists

KD Suarez
Cloud heights now lower by an average of 30-40 meters; Seen to help cool Earth down, countering global warming

LOWER CLOUDS. This image of clouds over the southern Indian Ocean was acquired on July 23, 2007 by one of the backward (northward)-viewing cameras of the Multi-angle Imaging SpectroRadiometer (MISR) instrument on NASA’s polar-orbiting Terra spacecraft. Photo courtesy of NASA/JPL-Caltech

MANILA, Philippines – A NASA-funded study by New Zealand scientists has discovered that our planet’s clouds have gotten lower in the past 10 years, with potential implications on our climate’s future.

NASA’s Jet Propulsion Laboratory (JPL) said on Tuesday, February 21, that scientists at the University of Auckland found that there has been an overall trend of decreasing cloud height in the past decade. The study had assistance from the US space agency.

Physicists Roger Davis, a professor at the university, and Matthew Molloy analyzed the measurements of clouds around the globe made by the Multiangle Imaging SpectroRadiometer (MISR) of the NASA Terra Satellite. The data covered the period March 2000 up to February 2010.

The study said the average height of clouds in the earth’s atmosphere declined by around 30 to 40 meters (100-130 feet), or by one percent. Fewer clouds at very high altitudes contributed mostly to the height differences, but the exact reason is still undetermined, said Davies.

Because of lower cloud heights, there could be a potential cooling effect on the planet, specifically because this could allow the earth to lower temperatures more efficiently. This more effective cooling could slow down the potential impact of global warming.

The researchers said this could be a possible “negative feedback” mechanism, where an effect of global warming would counteract it.

The study also revealed “a complex pattern of decreases in cloud altitude across some regions of the globe and increases in others,” including the effects of El Niño and La Niña in the Pacific.

The study will continue throughout the current decade to see if the cloud heights continue to decrease.

“This is the first time we have been able to accurately measure changes in global cloud height and, while the record is too short to be definitive, it provides just a hint that something quite important might be going on,” said Davies. – Rappler.com