The heavens are literally falling, scientists have claimed. Researchers have discovered that Earth's cloud cover has been gradually dropping for the past 10 years, lowering the height between the sky and the ground.

Researchers from the University of Auckland in New Zealand analysed heights of the Earth's clouds from 2000-10 and discovered that cloud levels over the Earth are falling. For their analysis, they used the multi-angle imaging spectroradiometer (MISR) instrument on Nasa's Terra spacecraft.

Researchers discovered that the height of the clouds had declined by close to 1 percent over the decade by between 100ft and 130ft (30-40 metres). They believe that reduction in cloud height would allow the earth to cool more efficiently. This reduction in height reduces the surface temperature of the planet and potentially slows the effects of global warming.

A team led by Roger Davies says that while the record is too short to be definitive, it is exciting scientists. Longer-term monitoring will be required to determine the significance of the observation for global temperatures.

According to the researchers, clouds are one of the biggest uncertainties in our ability to predict future climate. Cloud height is extremely difficult to model and therefore has not been considered in models of future climate. For the first time we have been able to accurately measure the height of clouds on a global basis.

"If cloud heights come back up in the next 10 years we would conclude that they are not slowing climate change," said Davies.

"But if they keep coming down it will be very significant. We look forward to the extension of this climate record with great interest. We don't know exactly what causes the cloud heights to lower," he said.