When it comes to repairing damage done to the Earth鈥檚 climate there鈥檚 no shortage of ideas, ranging from schemes to put 鈥渟unshades鈥� in orbit to burying the offending carbon dioxide underground.
But ideas won鈥檛 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.
鈥淭he ideas for how to change our climate keep getting pumped out. They get lots of column inches,鈥� says Boyd. 鈥淢y concern is that we will reach a , people will ask what are we doing about it, and none of the schemes will have been tested.鈥�
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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.
鈥泪蹿 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鈥檛 be too fussy and we will make mistakes,鈥� 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.
鈥淲e have only started to realise how complicated and interconnected Earth systems are, and scale up will be difficult,鈥� Boyd says.
For example, the Pinatubo volcanic eruption inspired the proposal to inject sulphur particles in to the atmosphere to alter the Earth鈥檚 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 鈥� for example seeding oceans with iron to stimulate algae that would suck up carbon dioxide 鈥� will be the most prone to unknown side effects, says Boyd. 鈥淵ou probably never want to work with animals, children or biological systems.鈥�
Risk management
The schemes that will be least prone to unexpected side effects 鈥� but potentially among the most costly 鈥� would be those based on well understood principles of physics and chemistry, such as 鈥渨ind scrubbing鈥�, 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. 鈥淵ou risk letting people of the hook in terms of reducing emissions,鈥� he says. 鈥淥n the other hand purposely manipulating the environment on such a huge scale is a frightening concept, and it could push people to take action.鈥�
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