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Storm clouds threaten central Auckland.
The University of Auckland has had its head in the clouds, and its conclusion is they are getting lower.
The university looked at ten years of data from Nasa's terra telescope to discover the average cloud height decresed by 1% over the past decade.
The telescope showed fewer clouds were occuring at higher altitudes.
Researchers believe a significant reduction in cloud height would lead to reducing the surface temperature of the planet and slowing global warming.
"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," explains lead researcher Professor Roger Davies.
He said longer-term monitoring will be required to determine the significance of the observation for global temperatures.
"We don't know exactly what causes the cloud heights to lower," Davies said, "but it must be due to a change in the circulation patterns that give rise to cloud formation at high altitude."
"Clouds are one of the biggest uncertainties in our ability to predict future climate," he said.
The paper - Global cloud height fluctuations measured by MISR on Terra from 2000 to 2010 - by Roger Davies and Bachelor of Science student Matthew Molloy from the University of Auckland has been published in Geophysical Research Letters.
