Tefnut's Environmental and Drought News Article
Updated February 26, 2012 12:09:19
New research has found clouds are dropping closer to the Earth, with scientists measuring their height for the first time on a global basis.
Experts from the University of Auckland suggest the change in cloud altitude could be the Earth's way of dealing with global warming.
In 1999, NASA launched its Terra satellite into space. On board was a Multi-angle Imaging Spectroradiometer (MISR).
It uses nine cameras at different angles to produce a stereo image of clouds around the world, allowing measurement of their altitude and movement.
Researchers at the university studied the measurements taken over a decade.
Lead researcher Professor Roger Davies says over the past 10 years clouds have lowered in altitude.
"About 30 to 40 metres, just depending on how you did it. And that's actually a little bit more than would be needed to compensate for the effective increased CO2 over the same 10 years," he said.
He says researchers are unsure why it is happening, but that it is most likely due to a change in the circulation of the atmosphere.
"You need to get rising air to form a cloud and if the winds aren't quite strong enough, then you won't get that. And so we suspect that's the cause but we don't know quite the details and how that was actually happening."
Professor Davies says if the clouds continued to drop, global warming would slow down.
"The C02's increasing all the time and that's tending to heat the planet up and raise surface temperatures, and this is a cooling mechanism," he said.
"It's not strong enough to make the temperatures come down again, but it may slow how quickly they rise."
He says in the next 10 years scientists will gain more confidence in whether the drop is a response by the clouds to surface temperatures.
"It could be just a one-off. It could be just a 10 years just doing the low thing and if it goes back up again then it wouldn't have such a strong effect," he said.
"So that's why we're going to be very interested in looking at this over the next 10 years."
But never fear, Professor Davies says our heads won't literally get to the point that they're in the clouds.
"What's going on at the moment is most of the clouds are just staying put. It's the ones that are very high up - we're seeing fewer very high clouds and there's only so many of those clouds up there and once they're gone they're gone and things will stay pretty stable," he said.
"But it would take a few hundred years before we ran out of these high clouds at the rate that they're coming down."
The research has been published in the journal Geophysical Research Letters.
Source: Australian Broadcasting Corporation
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