By Kieran Cooke, Climate News NetworkThis piece first appeared at Climate News Network.

LONDON — Geo-engineering of the climate is fraught with all manner of technical, ethical and governance issues but needs to be taken into consideration if targets for limiting global temperature increases are going to be met.

Steve Rayner, James Martin Professor of Science and Civilisation at Oxford University, UK, says that while climate geo-engineeering is at a “very early, imaginary stage” at present, it should neither be lauded as the potential saviour of humanity nor dismissed as completely fanciful.

Climate geo-engineering is defined as the deliberate large-scale manipulation of the planetary environment in order to counteract anthropogenic climate change. In an Oxford lecture Professor Rayner said various ideas were being put forward – each with its own set of challenges and potential problems.

Solar radiation management includes putting giant mirrors into space in order to deflect sunlight. This has considerable disadvantages – not least the vast cost and enormous technical difficulty of lifting such devices up into orbit.

Another scheme involves sulphate particulate injection into the stratosphere: backers of this idea say it is the most cost-efficient method and would, like the impact of an exploding volcano, produce cooling most rapidly (see our story of 4 March, Volcanoes may mask ‘lost’ warming).

Who would decide?

Other scenarios include machines to suck CO2 out of the atmosphere, and schemes to enrich tracts of the world’s seas with iron in order to enhance their role as a carbon sink.

“Generally these ideas are seen as a complement to and not a substitute for adaptation and mitigation”, says Rayner. “And the challenges are enormous.

“For example, to put the sulphate injection idea into action would mean we would have to create an enterprise something on the scale of the global cement industry.”

Issues of governance and ethics are even more challenging than the technical aspects of climate geo-engineering. There is the question of what sort of consent would be needed to do something on a global scale – a global treaty would likely be needed.

Then there is the issue of what would happen if something went wrong with a project – and who would pay to put it right? Perhaps referenda would be needed to ensure public approval and participation in such schemes.

“Is there something fundamentally unethical about interfering with nature?” asked Rayner. Many had already concluded that climate geo-engineering was dangerous – crazy and incompatible with democracy, he said.

Professor Rayner is among a team of scientists and academics who have drawn up a set of guiding principles for climate geo-engineering. Such principles include full disclosure, independent assessment of the impacts of such projects, and public participation at each stage of decision-making.

“Unlike the case of the pharmaceutical industry, the negatives as well as the positives at each stage of research must be published”, said Rayner.

He said that within the scientific and engineering community he had generally found an overwhelming reticence on climate geo-engineering, and even on the idea of doing any research into it.

“Some would prefer not to talk about climate geo-engineering at all”, Rayner told the Climate News Network. “But the general consensus is that on the present trajectory of emissions it’s not possible to meet targets limiting global temperature rises.

“We do need research and investigation”, he said. “It all needs careful governance – transboundary issues need particularly careful attention. Above all, hubristic claims should be avoided – the watchword is caution.”

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