Scholars propose a legal framework to mitigate the risks of solar geoengineering.
A high-pressure cell stalls against the Himalaya. The heat climbs beyond what the human body can withstand. Twenty million perish across India. In the aftermath, the Indian government unilaterally injects reflective aerosols into the upper atmosphere—what scientists call stratospheric aerosol injection (SAI)—dimming the sun above India and, as the particulates spread, the globe.
This disaster is, mercifully, drawn from the opening chapters of Kim Stanley Robinson’s 2020 novel The Ministry for the Future. But, in a recent article, Craig Martin of the Washburn University School of Law and Scott Moore of the University of Pennsylvania argue that such a scenario cannot be dismissed as mere fiction. Martin and Moore warn that, as the world heats, the likelihood and risks of unilateral SAI will only grow.
Climate change is here. The early 2020s, Martin and Moore note, marked the explosion into the public consciousness of climate change as a “clear and present danger.” But as its effects increase in speed, intensity, and scale, the political obstacles to tackling the root cause of climate change—greenhouse gas emissions—appear intractable, they explain.
Political and policy institutions are increasingly considering various forms of solar geoengineering—technological attempts to limit the warming effects of solar radiation—as interim responses to the climate crisis. Of these, Martin and Moore observe that SAI receives the most attention. Its appeal, they suggest, is apparent: SAI is effective, technologically feasible—even for moderately developed nations—and “orders of magnitude cheaper” than other responses to climate change.
Yet SAI carries profound risks. These include environmental dangers—changes in rainfall, ocean acidification, and ozone depletion—with vast potential effects on agriculture, aquaculture, and ecosystems worldwide. Other risks are political: With the immediate consequences of emissions deferred, global progress on the causes of climate change might slow or grind to a halt, Martin and Moore warn.
Some nations stand to gain enormously from an immediate drop in global temperatures, but the costs of SAI will be felt worldwide. This imbalance, Martin and Moore argue, creates what economists call a free-driver problem. They explain that the low cost and quick impact of SAI make unilateral action tempting: The deploying nation enjoys immediate relief while the world shoulders the risks.
Martin and Moore acknowledge that general principles of international law and various international treaties relating to climate and the environment could, in theory, constrain the deployment of SAI by individual nations. Practice, however, is another matter. One problem Martin and Moore note is enforcement—a perennial weakness of international law. They add that even when the international community is willing and able to prohibit SAI, enforcement generally punishes rather than prevents unilateral wrongdoing. Martin and Moore argue that, as climate change worsens, it becomes more and more likely that a nation facing devastating heat will find uncertain sanctions preferable to certain catastrophe.
Unilateral SAI also poses a key second-order risk, Martin and Moore contend. They explain that nations facing food-system disruption, population displacement, and extreme weather caused by another state’s unilateral actions are unlikely to stop at diplomatic or economic countermeasures. Martin and Moore warn that international law governing the use of force will do little to constrain a state determined to protect its national security.
Both the nations that stand to gain from SAI and those that stand to lose are likely, Martin and Moore suggest, to find it more attractive to beg for forgiveness than permission. Constraints on SAI deployment are urgently needed, they conclude—not only to ensure its responsible use but also to prevent “the eruption of armed conflict.”
To meet that need, Martin and Moore call for a treaty-based framework focused solely on SAI. They emphasize that this system must establish binding commitments and a formal institutional structure to monitor, enforce, and prohibit unilateral action. Looking to other international regimes tasked with regulating existential risks—such as nuclear non-proliferation and ozone-layer protection treaties—Martin and Moore argue that an SAI-governance framework should also oversee research and experimentation and mandate collective decision making.
Martin and Moore stress that legitimacy is foundational. They insist any SAI-governance framework must be transparent and accountable. Equity and fair representation—established principles of international law—should guide the distribution of the costs and benefits of decisions. Martin and Moore caution that a legal regime lacking this legitimacy could invite the very unilateralism it aims to avoid.
To move quickly, Martin and Moore recommend developing an SAI-focused governance framework within an existing international institution. They suggest two candidates: the Montreal Protocol, if amended to cover SAI, and the United Nations Framework Convention on Climate Change, a potentially robust forum for negotiation and oversight. Either option, Martin and Moore suggest, would avoid starting from scratch while benefiting from the legitimacy and expertise of these well-respected institutions.
Martin and Moore urge swift action to limit the risks of ecological devastation, geopolitical instability, and armed conflict. They conclude that the development of SAI-specific international law offers the best chance to avoid the dangers of unilateral action in a fast-warming world.
