Control

Of the three kinds of political dilemmas regarding geoengineering, this is probably the easiest to grasp.

The question of control over geoengineering parallels to a surprising degree the question of control over (or legitimacy of) warfare: both emerge from considerations of a nation's ability to survive. It's reasonable to assume that the United Nations would expect to authorize and provide oversight for any re-terraforming project: the benefits would be transnational, so the costs should arguably be spread; the risks are transnational as well, so international oversight helps to defray blame; and given the scale of such projects, nations that would be affected one way or another would demand consultation.

But like warfare, it's entirely possible that a state with the capacity to undertake such a project independently might decide that international restrictions are irrational, or that its survival is so threatened that the bureaucracy of a transnational body is unacceptable. Smaller nations following such a course would be declared "rogue nations" (and are addressed below); when a hegemonic nation does it, such as the United States or China, there may be little the international community can do in response.

Little, unless rival hegemonic powers come to believe that such independent geoengineering efforts threaten their security and environmental survivability. Then, like any other security threat, this could be a trigger for war.

Liability

There's very little doubt that any geoengineering efforts begun without sufficient study could have a significant chance of triggering unforeseen results, simply due to the complexity of the geophysical systems involved. In a situation of imminent risk of (say) Greenland's ice sheet collapsing into the ocean, such unforeseen results may be an acceptable trade-off for avoiding certain disaster (to be clear, I don't think we're likely to see Greenland's ice sheet showing signs of imminent collapse within the decade, but it's precisely the kind of situation that would push even opponents of geoengineering to consider its use). But geoengineering strategies can have dangerous externalities. Take the solution Dr. Caldeira suggests for discussion in the Times:

What can be done? One idea is to counteract warming by tossing small particles into the stratosphere (above where jets fly). This strategy may sound far-fetched, but it has the potential to cool the earth within months. [...] If we could pour a five-gallon bucket’s worth of sulfate particles per second into the stratosphere, it might be enough to keep the earth from warming for 50 years. Tossing twice as much up there could protect us into the next century.

Sulfate particles can be found in the atmosphere as the result of volcanos and human industrial activity, and can measurably reduce radiative forcing. Sulfate particles are not benign, however, and can be linked to a variety of human diseases, as well as to acid rain and changes to cloud formation. Pumping more sulfate particles into the air -- even high up -- is highly likely to lead to greater incidences of these problems.

Such problems resulting from sulfate particles would not be limited to the nation or nations leading the project; neither is it likely that they'd be distributed evenly around the globe. It's highly likely, instead, that the problems resulting from pumping five gallons of sulfate particles per second into the atmosphere for an extended period would affect some nations more than others. If history is any guide, the nations most likely to bear the burden of these health and environmental problems are those that are the poorest and least stable. Will the countries and institutions pushing for the geoengineering strategy be equally as eager to pay for reparations and recovery?

This assumes that everything goes as expected. If there's an accident, or a wildly destructive unanticipated side-effect, the financial, environmental and human costs could be dramatically higher.

(This raises the interesting possibility that the insurance industry -- especially the re-insurance companies -- may exert tremendous pressure on governments and institutions not to adopt a geoengineering strategy as anything but a final fall-back.)

Rogue Projects

The first two political dilemmas arising from geoengineering efforts are heightened versions of relatively conventional international issues: political control and distribution of costs. The third dilemma, conversely, has few precedents.

It is possible that, should the international community refrain from geoengineering strategies, one or more smaller, non-hegemonic, actors could undertake geoengineering projects of their own. This could be out of a legitimate fear that prevention and mitigation strategies would be insufficient, out of a disagreement with the consensus over geoengineering safety or results, or -- most troublingly -- out of a desire to use geoengineering tools to achieve a relative increase in competitive power over adversaries.

It's entirely possible, even likely, that the hegemonic international powers will decide, after careful study, that the potential risks of substantive geoengineering outweigh the potential benefits, and that no such strategies should be pursued. However, we know that the negative impacts of global warming are distributed unevenly, and what may be acceptable levels of climate disruption for the major states may be utterly devastating for poorer, smaller nations. It is in this context that a scientifically-powerful developing nation -- India or Brazil, for example -- may decide that it is unwilling to abide by UN decisions about re-terraforming, and begin to undertake such a strategy.

It may have concluded that the impacts of climate change would hit it too quickly for carbon reductions around the world to have an effect; it may see geoengineering as its only choice. Conversely, it may have concluded that the scientific arguments against geoengineering were faulty, and that such an effort could be undertaken safely, regardless of the success of other solutions. Would this rogue effort be backed up by a threat to use all means necessary to defend the project? Would the UN or the hegemonic powers be willing to use sanctions, interdiction of project-related materials, even war to stop the rogue?

Moreover, with the geoengineering technologies on the table, there's no guarantee that they'll only be used for environmental purposes.

As nuclear proliferation and open-source warfare make conventional war effectively obsolete, geoengineering weapons may offer the potential to disrupt one's enemies over a long, subtle campaign. As I put it earlier this year:

No nation that sees itself as a great power is going to be willing to risk having its climate and environment completely in the hands of another nation. Research into methodologies for geoengineering will happen simply out of self-preservation -- after all, nobody wants to fall victim to a "terraforming gap."

Imagining the Unthinkable

Finally, we have to recognize that the "rogue actors" need not be states. While the costs of geoengineering strategies may be enormous, they wouldn't necessarily be out of the range of some of the global billionaires. The movie scenario's not hard to imagine:

In a world on the verge of destruction... while nations delay and scientists bicker... one man sees a way to save us all.

"But the UN hasn't decided on liability and safety!"

"I don't care about the UN, I care about the world!"

As the planet burns, Warren Gates-Branson III crosses the line no nation dares cross.

"All my money counts for nothing if the world's gone to hell!"

He is... THE TERRAFORMER.

Unfortunately, the less-heroic version's not hard to imagine, either: a cadre of scientists and engineers willing to say anything to test out pet ideas, a multi-jillionaire who believes himself smarter than those bureaucrats at the UN, and a planet already on the tipping point of catastrophe, just waiting for some kind of event to trigger an unstoppable cascade of environmental tragedy.

(To quote Dr. Farnsworth, "oh, I made myself sad.")

...

When I argue that we need to start studying geoengineering now, I don't simply mean the climate scientists and geophysicists. I mean everyone who worries about policy, embraces activism, works with NGOs and movements, or considers herself or himself a stakeholder in the well-being of the planet. If we ignore this possibility, decisions will be made without our consent, even without our knowledge. We need to understand the kinds of choices we'll face if we continue to delay action on global warming. Geoengineering might, with the wrong moves, be catastrophic; it might, with the right knowledge and technologies, be our final hope. But it must not be a decision made by ideology, or as a military maneuver, or out of convenience.