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Engineers are looking at ways of reversing global warming
- not by lowering the carbon dioxide that causes it, but through
'geoengineering', literally changing the face of the
Earth to shed heat.
'If we can warm the planet, can we also cool it?'
- was the title chosen for a session at the AAAS
that was marked as much by tensions between the 'for' and
against' camps making presentations, as by attempts to
explain what geoengineering actually involves.
Geoengineering represents attempts to cool the planet by
making changes to the Earth’s surface or to the atmosphere
or to clouds. A simple example would be to paint black road
surfaces white in order to reflect back solar radiation. Another
is 'carbon capture' - taking carbon dioxide directly
out of the atmosphere as a way to halt or reverse global warming.
The panel was discussing more radical approaches, such as
introducing substances into the atmosphere to bring about
global cooling.
Dr Ken Caldeira of Stanford University, who was in favour
of the geoengineering approach, described some of the ideas
being studied. One involved the spraying of sulphur dioxide
into the upper atmosphere where it would reflect away solar
radiation, in much the same way that the sulphur discharges
from a volcano do.
Another approach would see aluminium particles spread into
the atmosphere, again to reflect away radiation.
None of these techniques are being applied at the moment,
however, as researchers attempt to study the long-term implications
of tampering with something as fundamental as our atmosphere.
“Most of the work going on now is modelling,” Dr Caldeira
said.
Prof Martin Bunzl of Rutgers University acknowledged that
the use of sulphur might be expected to lower average global
temperatures by about 2 degrees - but what other effects this
approach might cause were unknown.
Nor could you switch off the effect quickly if it was discovered
to cause harm. Temperatures would have to be brought back
slowly to avoid causing environmental problems. He also dismissed
the idea that these techniques could be applied on a small-scale
basis, saying - “I don’t believe we can assess the true risk
unless we go to a global scale.”
Prof Brad Allenby of Arizona State University was also dismissive
of the geoengineering approach. The fractious nature of the
panel debate showed “how sketchy our knowledge of geoengineering
is,” he said. To pursue these ideas was “extraordinarily naive
and extremely dangerous”.
Dr Philip Rasch of Pacific Northwest National Laboratory
in Washington state said the ideas should be discussed in
“an open dialogue”. He did not advocate immediate use of geoengineering,
but believed it should be researched so all options were known.
Source - The Irish Times
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