The National Research Council recently put out a report on geoengineering as a way to moderate climate change. This report was sponsored by the National Academy of Sciences, U.S. intelligence community, National Aeronautics and Space Administration, National Oceanic and Atmospheric Administration, and U.S. Department of Energy. Thus, there is a lot of heft behind this report.

The University of Michigan’s Atmospheric Science Professor Joyce Penner served on the committee, so I saw an article on it in the UM University Record by Nicole Casal Moore that I thought was very well done. Here are some key excerpts, which I made into bullet points:

• Techniques to remove CO2 include restoring forests and adopting low-till farming—both of which trap carbon in plants and soils. Oceans could be seeded with iron to promote growth of CO2-consuming organisms. And carbon could be be sucked directly out of the air and injected underground.
• Methods to reflect sunlight include pumping sulfuric compounds into the stratosphere to, in essence, simulate a volcanic eruption; and spraying sea water mist or other finer-than-usual particles over the ocean.
• The scientists caution against dumping iron in the oceans, as the technical and environmental risks currently outweigh the benefits. Similarly, they warned against sunlight-reflecting approaches, also known as “albedo modification.”
• Even in its opposition to sunlight reflecting tactics, the committee still recommended more research into them, as it urged more study of all climate intervention possibilities. Penner was struck by this call to action.
• “U.S. agencies may have been reluctant to fund this area because of the sense of what we call ‘moral hazard'—that if you start down the road of doing this research you may end up relying on this or condoning this as a way of saving the planet from the cost of decreasing CO2 emissions,” Penner said. “But we’ve stated that decreasing emissions must go hand in hand with any climate intervention efforts.
• "We need to develop the knowledge base to allow informed decisions before these dangerous effects are upon us,” she said.

Comments: The big news is that the scientists on the committee reject the idea that we should avoid research into geoengineering for fear that such research is part of a slippery slope. However great the problems and disadvantages of certain techniques geoengineering, there are possible futures in which we might need them very badly. So we must risk knowing what we can about them rather than trying to keep ourselves in ignorance to prevent such techniques from being used. 

Among the techniques, anything done on land–such as low-till farming and sequestration–hold no terrors. Human beings have modified the land for many centuries; and any reduction in carbon dioxide from such efforts just slows down our move into uncharted territory. But modifying the oceans or the clouds would take us into uncharted territory in yet other directions, and so is something we should go slow on.

Much of the harm of climate change may not be about global warming per se but about the fact that global warming will make the climate different in the future than it has been in the past. Entropically, to the extent that the places people live are adapted to the current climate, different tends to be worse until very substantial adjustment costs have been incurred. Modifying the clouds along the lines of some geoengineering proposals may make the Earth cooler, but is almost certain to cause the climate to be different from what it has been in the past, creating costs of climate change even if it arrests global warming.  

As for seeding the oceans with iron, this might have little effect on the climate other than through the desired reduction in carbon dioxide in the atmosphere, but it could easily have unforeseen effects on the ecology of the oceans. However, the acidification of the oceans from higher carbon dioxide concentrations is also taking us into uncharted territory for ocean ecologies. So seeding the ocean with iron to increase carbon dioxide takeup by ocean life could at some point be the safer course even for ocean ecologies. We may need to know how to make this judgment sooner than we would like. Hence the urgency of research. 

Update: Nichol Brummer tweeted to say that he has a new website in beta on enhanced Olivine weathering to chemically combine carbon dioxide to form carbonate. This is a promising approach.