"When it comes to repairing damage done to the Earth's climate there's
no shortage of ideas, ranging from schemes to put "sunshades" in orbit
to burying the offending carbon dioxide underground.
But ideas won't be enough, so there is an urgent need to rank those
proposals to work out which should undergo rigorous testing, argues
Philip Boyd of the National Institute of Water and Atmospheric
Research in Dunedin, New Zealand.
"The ideas for how to change our climate keep getting pumped out. They
get lots of column inches," says Boyd. "My concern is that we will
reach a tipping point, people will ask what are we doing about it, and
none of the schemes will have been tested."
Boyd proposes that an international body such as the Intergovernmental
Panel on Climate Change prioritise the schemes according to possible
risks involved, how quickly they could be got of the ground, their
cost, and how efficiently they would change the climate.
Climate scientist Martin Manning of the University of Victoria in
Wellington agrees that a systematic ranking is needed, in part because
there is little communication between research communities working on
different approaches.
"If warming is to be kept at 2 degrees or so, which is what most
governments are endorsing, we have to take every technology on hand,
we can't be too fussy and we will make mistakes," he says.
Herculean task
Any assessment should be broadened to include other techniques besides
geo-engineering, such as using plants for sequestration, says Manning,
who worked for the IPCC during the last assessment.
Some schemes could quickly be dismissed, but testing even one of the
feasible schemes will still be a herculean task.
"We have only started to realise how complicated and interconnected
Earth systems are, and scale up will be difficult," Boyd says.
For example, the Pinatubo volcanic eruption inspired the proposal to
inject sulphur particles in to the atmosphere to alter the Earth's
albedo so that sunlight is reflected back into space. But closer
scrutiny of the eruption revealed that sulphur particles alone can not
account for the fall in temperatures and other changes in climate that
followed the eruption.
Schemes that rely on biological mechanisms – for example seeding
oceans with iron to stimulate algae that would suck up carbon dioxide
– will be the most prone to unknown side effects, says Boyd. "You
probably never want to work with animals, children or biological
systems."
Risk management
The schemes that will be least prone to unexpected side effects – but
potentially among the most costly – would be those based on well
understood principles of physics and chemistry, such as "wind
scrubbing", in which chemicals are used to absorb carbon dioxide from
the atmosphere.
Boyd ranks geochemical schemes, such as transforming the carbon in
carbon dioxide into bicarbonate ions that would be dissolved in the
ocean as in between the two when it comes to risks of unexpected side
effects.
Boyd acknowledges that there are other risks inherent in testing
mitigation schemes. "You risk letting people of the hook in terms of
reducing emissions," he says. "On the other hand purposely
manipulating the environment on such a huge scale is a frightening
concept, and it could push people to take action."
Journal reference: Nature Geoscience, DOI: 10.1038/ngeo348
Climate Change – Want to know more about global warming: the science,
impacts and political debate? Visit our continually updated special
report."
Taken from New Scientist at http://environment.newscientist.com/article/dn15037-ranking-methods-to-save-the-world.html?DCMP=ILC-hmts&nsref=specrt10_head_Survival%20tips
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