Study: Geoengineering Clouds Could Backfire
Radical plan to combat global warming
'may raise temperatures'
The Independent (U.K.), June 7, 2010
A controversial proposal to create artificial white clouds over the
ocean in order to reflect sunlight and counter global warming could make
matters worse, scientists have warned.
The proposed scheme to create whiter clouds over the oceans by
injecting salt spray into the air from a flotilla of sailing ships is
one of the more serious proposals of researchers investigating the
possibility of "geoengineering" the climate in order to combat global
warming.
Geoengineering - deliberately altering the global climate - was
dismissed as outlandish fantasy a decade ago but has recently been seen
as a serious topic of study, given the international failure to curb
global emissions of carbon dioxide and the possibility of extreme
climate change.
However, a study into the effects of creating man-made clouds which
reflect sunlight and heat back into space has found that the strategy
could end up having the opposite effect by interfering with the natural
processes that lead to the formation of reflective white clouds over the
ocean.
A team of scientists from Britain and Finland found that spraying salt
water into the air to encourage the formation of clouds may actually
hinder natural cloud formation over the coastal regions of the
continents because of other pollutants from industrial activities.
"Our research suggests that attempts to generate brighter clouds via
sea spray geoengineering would at best have only a tiny effect and could
actually cause some clouds to become less bright," said Professor Ken
Carslaw of the University of Leeds.
White clouds form naturally over the ocean as a result of saltwater
spray being blown high into the air. The salt crystals form tiny
particles on which cloud droplets form and the denser the droplets, the
whiter the cloud and the more reflective it is towards incoming
sunlight.
Twenty years ago, scientists proposed that it might be possible to
augment this process with a fleet of ships designed to spray saltwater
into the air. Calculations suggested that this could cool the planet if
carried out on a large enough scale.
However, a computer model used by Professor Carslaw and his colleagues
suggested that it would be difficult to create a uniform layer of
saltwater spray and that natural particles in the air, called aerosols,
could interfere with the process. "The formation of clouds from
artificial sea spray is particularly sensitive to background levels of
aerosol. This means that injecting spray around coastal areas where
there is a lot of air pollution from land may not produce enough extra
cloud drops to stave off global warming," Professor Carslaw said.
"In some locations, the artificial spray particles may hinder natural
drop formation and could have an opposite effect on climate to that
intended. In practice, generating a uniform covering of reflective
clouds over large regions of the world's oceans would be extremely
challenging," he said.
Geoengineering
Artificial clouds
This notion involves augmenting the natural process of white-cloud
formation over the oceans to reduce levels of incoming sunlight and
heat. But it would not help the increasing acidity of the seas because
it fails to address rising levels of carbon dioxide in the atmosphere.
Artificial volcanoes
Another idea is to emit sulphate particles high into the atmosphere to
reflect sunlight back into space. These would simulate what happens in a
volcanic eruption when the aerosol particles from the eruption cut out
sunlight and cause limited global cooling. The sulphates would wash out
within a couple of years but again this "solution" does not address
ocean acidity, or the potential acidity of the sulphate aerosols.
Artificial trees
Being able to emulate the way trees convert carbon dioxide gas into
solid carbon-containing substances is seen as the best geoengineering
idea. But nobody has been able to do it better than trees - so why not
simply plant more forests? This proposal reduces carbon dioxide
concentrations and so helps ocean acidity.
Mirrors in space
The idea is to create a huge reflective surface between earth and the
sun that could be adjusted to interfere with incoming solar radiation.
Apart from the immense technical difficulties, the political
implications of who controls this technology are problematic to say the
least.
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