Researchers at the University of Auckland have discovered that Earthâ€™s clouds have been getting lower for the past 10 years. Although it is too early to make any definitive conclusions from the data, lead researcher Roger Davis said that lower clouds could be indicative of something quite important for the Earthâ€™s climate.
The researchers have been studying the Earthâ€™s clouds for the past ten years using data gathered from the Multi-angle Imaging SpectroRadiometer (MISR) on NASAâ€™s Terra spacecraft. MISR uses multiple angles from nine cameras to produce a stereo image of clouds around the globe. These images are then used to measure the altitude and movement of the Earthâ€™s clouds.
Researchers found that cloud height has dropped by about 1% around the globe over the past ten years, or about 100 to 130 feet (30 â€“ 40 metres).
A continual reduction in cloud height would reduce global average temperatures by allowing the Earth to cool to space more efficiently. This would thus represent a â€œnegative feedbackâ€ mechanism â€“ a change caused by climate change that works to counteract it. Another negative feedback was discovered earlier this year over China due to the stratospheric aerosols resulting from coal combustion.
The researchers are still unsure what is causing the cloud heights to lower, but they hypothesize that changing circulation patterns are altering cloud formation at higher altitudes. Clouds represent one of the biggest uncertainties in climate models, and understanding what effect they have on global temperatures will help scientists predict how severely the Earthâ€™s climate will change.
In the meantime, Daviesâ€™ team will continue to monitor the Earthâ€™s clouds to determine whether their height will continue to decrease over time.
Image CC licensed by John Johnston: Clouds and moon over Auckland, New Zealand