A blue-ribbon panel convened by England's Royal Society issued a report earlier this week that considers engineering methods to counteract the warming effects of increased greenhouse gas emissions. Though it advocates closer attention and much more research on such techniques, the report’s attitude is decidedly cautious: "Far more detailed study would be needed before any method could even be seriously considered for deployment” on a large scale, writes Cambridge University physicist and Royal Society President Martin Rees, in introductory comments. Moreover, says Rees, "none offers a 'silver bullet' "
The rationale for exploring ways of counteracting the effects of greenhouse gases is forcefully stated at the outset. "Climate change is happening. Its impact an cost will be large, serious, and unevenly spread. The impacts may be reduced by adaptation, and moderated by mitigation, especially by reducing emissions of greenhouse gases. However, global efforts to reduce emissions have not yet been sufficiently successful to provide confidence that the reductions needed to avoid dangerous climate change will be achieved."
The report distinguishes between methods that remove greenhouse gases from the atmosphere and techniques that modify solar irradiation of the earth's surface and atmosphere. In principle, it says, carbon dioxide removal is the preferable approach because it is much less risky, in effect taking earth back to its "natural" state--that is to say, the state it would be in if it were unaffected by man-made carbon emissions. But such techniques are slow-acting and, as yet, "none has yet been demonstrated to be effective at an affordable cost, with acceptable side effects."
Radiation management techniques--seeding the atmosphere with reflective aerosols, for example--are by comparison cheaper and faster. But they would require striking a delicate and subtle balance between the effects of increased carbon concentrations and counter-acting measures, a balance moreover that would have to be maintained and sustained over centuries, stretching global governance well beyond what we are able to do today. Because of their riskiness and the immense political challenges they pose, "solar radiation management methods should not be applied unless there is a need to rapidly limit or reduce global average temperatures."
The Royal Society recommends that the United Kingdom inaugurate a research program into geoengineering techniques, but it's takeaway message really is this: if you've been thinking that carbon counter-action could be easier than carbon reduction, you have another think coming.