Nature calls for serious consideration of geoengineering in their lead-off editorial this last week.
"The latest scientific research suggests that even a complete halt to carbon pollution would not bring the world’s temperatures down substantially for several centuries. If further research reveals that a prolonged period of elevated temperatures would endanger the polar ice sheets, or otherwise destabilize the Earth system, nations may have to contemplate actively removing CO2 from the atmosphere. Indeed, the United Nations Intergovernmental Panel on Climate Change is already developing scenarios for the idea that long-term safety may require sucking up carbon, and various innovators and entrepreneurs are developing technologies that might be able to accomplish that feat (see page 1094). At the moment, those technologies seem ruinously expensive and technically difficult. But if the very steep learning curve can be climbed, then the benefits will be great.
More radical still is the possibility of cooling the planet through some kind of ‘geoengineering’ that would dim the incoming sunlight (see page 1097). The effects of such approaches are much more worrying than those of capturing carbon from the air, however. The cooling from geoengineering would not exactly balance the warming from greenhouse gases, which would cause complications even if the technology itself was feasible — something for which the evidence has been circumstantial, at best.
But discussions about the possibilities offered by geoengineering could also lull the world’s leaders into complacency — if they lead them to believe that the technology will provide an escape hatch if the climate ever does reach a tipping point. This does not mean that the discussions should be avoided, but rather that the speculations need to be backed up with a solid body of research. Moreover, geoengineering research should be framed not as a hope for deus ex machina fixes to sudden global deterioration, but as a palliative cushion for the worst excesses of the peak years that are inevitable even after emissions start to be cut. A world slightly shaded from the Sun while its carbon levels are brought down by means of active capture would be a strangely unnatural place — but not necessarily a bad one, compared with the alternatives."