Chicken Licken was right, the sky really is falling. Nasa satellite data has shown that the Earth's cloud tops have been lowering over the last decade.
Cloud-top height fell one percent on average between March 2000 and February 2010, according to measurements from the multi-angle imaging spectroradiometer mounted on Nasa's Terra satellite. That one percent means a reduction of 30 to 40 metres in the average maximum height of clouds, during the 00s.
While the short record means it's difficult to draw any strong conclusions from the data, it does hint towards a longer-term trend. Roger Davies, the lead researcher on the project, warns that it's something that should be monitored in the coming decades to determine how significant it is for global temperatures.
If there is indeed a consistent reduction in cloud height, and this isn't just natural variability, then Earth would begin cooling to space more efficiently, reducing the surface temperatures and slowing the effects of climate change.
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"We don't know exactly what causes the cloud heights to lower," says Davies. "But it must be due to a change in the circulation patterns that give rise to cloud formation at high altitude." The Terra spacecraft, which launched in 1999 and records three-dimensional images of clouds around the globe, will continue gathering data in the coming years.
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