A new analysis of 15 years of NASA satellite cloud measurements finds that clouds worldwide show no definitive trend during this period toward decreasing or increasing in height. The new study updates an earlier analysis of the first 10 years of the same data that suggested cloud heights might be getting lower.
Clouds are both Earth's cooling sunshade and its insulating blanket. Currently their cooling effect prevails globally. But as Earth warms, the characteristics of clouds over different global regions -- their thickness, brightness and height -- are expected to change in ways that scientists don't fully understand. These changes could either amplify warming or slow it. Pinning down some of the uncertainties around clouds is one of the biggest challenges in determining the future rate of global climate change.
A new analysis of 15 years of NASA satellite cloud measurements finds that clouds worldwide show no definitive trend during this period toward decreasing or increasing in height. The new study updates an earlier analysis of the first 10 years of the same data that suggested cloud heights might be getting lower.
Clouds are both Earth's cooling sunshade and its insulating blanket. Currently their cooling effect prevails globally. But as Earth warms, the characteristics of clouds over different global regions -- their thickness, brightness and height -- are expected to change in ways that scientists don't fully understand. These changes could either amplify warming or slow it. Pinning down some of the uncertainties around clouds is one of the biggest challenges in determining the future rate of global climate change.
The study used data from the Multi-angle Imaging Spectroradiometer (MISR) instrument on NASA's Terra satellite. Using nine cameras pointing at Earth at different angles, it records images in four visible and near-infrared wavelengths. The images allow researchers to distinguish the amounts, types and heights of clouds. Launched in December 1999 with a planned six-year mission life, MISR was built and is operated by NASA's Jet Propulsion Laboratory in Pasadena, California.
Five years ago, Roger Davies, Buckley-Glavish professor of climate physics at the University of Auckland, New Zealand, and a colleague analyzed the first 10 years of MISR data. Their results suggested that cloud heights had lowered over the decade, raising the possibility that climate change effects on clouds might already be discernible.
Read more at NASA Jet Propulsion Laboratory
Image: Climate change may eventually change global cloud heights, but scientists need a longer data set to know whether that's happening already. Credit: NASA
