Solar geo-engineering is one proposed approach to mitigating the effects of climate change - the idea being to deflect some of the sun's incoming radiation. 

Ignoring the technology issues, in a world where countries can't even agree they contribute to greenhouse gases, the political uncertainties and geopolitical questions about who would be in charge of solar geo-engineering activity and its goals are daunting. A UN of climate change is the worst of all possible worlds. 

Social authoritarianism may be the way to go, according to modeling work from Carnegie's Katharine Ricke and Ken Caldeira and Juan Moreno-Cruz from the Georgia Institute of Technology. Their game-theoretic computer model found that a suitably powerful coalition would have incentive to exclude other countries from participating in the decision-making process about geo-engineering Earth. 

Though carbon dioxide emissions from the burning of coal, oil, and gas have decreased in developed nations, they have been increasing over the past decades due to greater emissions by developing nations. Feedbacks aside, no one disagrees that CO2 is bad. The idea behind solar geoengineering is to constantly replenish a layer of small particles in the stratosphere - basically duplicating the effect of volcanic eruptions, which scatter sunlight back into space.

"Attempts to form coalitions to reduce greenhouse gas emissions have repeatedly hit the wall, because it's difficult to get everybody to participate in a substantive and meaningful way," Ricke said. "Members of coalitions to reduce emissions have incentives to include more countries, but countries have incentives not to participate, so as to avoid costs associated with emission reduction while benefiting from reductions made elsewhere."

The model developed by Ricke, Caldeira and Moreno-Cruz found that when it comes to geoengineering, the opposite is true. Smaller coalitions would be more desirable to the participants, not less, because those members could set the target temperature to their liking without having to make everyone happy.

And excluded countries would want to 'get with the program' if they they could move the thermostat in the direction that better suits their interests. Since the costs of geoengineering are lower than mitigation, once a coalition has formed and has successfully implemented geoengineering, it would have an incentive to exclude permanently other willing participants.  

"My view, aside from any technical result, is that it should remain a central goal to maintain openness and inclusiveness in geoengineering coalitions, so that all people who want a voice in the decision-making process are able to have that voice," Caldeira said.

 Published in Environmental Research Letters.