Article
Unilateral Deployment: Could a Single Country Change the Global Climate?
Given how inexpensive and powerful some sunlight reflection methods, also known as solar radiation modification (SRM), appear to be, some worry that a single country, or even a rich individual, could change the global climate on their own. How large is the risk of a rogue or unilateral deployment of SRM?
Key takeaways
- It is possible that an individual country or other actor could deploy SRM unilaterally without consulting others.
- Only a small set of countries would be able to deploy SRM unilaterally at a large enough scale to substantially change the global climate.
- Powerful countries that could deploy SRM on their own will be subject to significant constraints that would reduce the incentives to act unilaterally.
A recurring fear about SRM is the prospect of unilateral deployment in which one country, or other actor, seeks to cool the planet without involving others in the decision-making.1 Other countries might regard this decision as unjust or its outcome as unfair and respond in some way.
How big is the risk of unilateralism, and what could it result in?
Unilateralism and its possible consequences
Unilateral deployment would entail one actor implementing SRM in the absence of broad, multilateral agreement.2 Imagine if the United States (US) announced it had begun a large, global stratospheric aerosol injection (SAI) deployment without telling any other countries beforehand.
Stratospheric aerosol injection (SAI)
Tiny particles released in the stratosphere would directly reflect a small fraction of sunlight.
Sunlight
This would understandably shock the rest of the world, for whom such a step would likely be viewed as illegitimate. And it could provoke a wide array of retaliatory responses – economic sanctions, diplomatic isolation, and perhaps even military strikes – from other states acting individually or in concert.
Having opened the door to SRM, such unilateral deployment might also cause other countries to pursue their own unilateral deployments, perhaps because they desire a larger amount of cooling (See note below on the “free driver” problem).
Such events would disrupt the international system and could destabilise world politics. For these reasons, the possibility of unilateral deployment of SRM has long been a serious concern.3
Who could deploy unilaterally?
Assessing the risk of unilateral deployment starts with identifying which actors would be capable of unilateral deployment, which depends on the technology and scenario considered. When it comes to sustained large-scale deployment of SAI – the type that generates most concern regarding unilateralism – the list of capable actors is short.4
Technical requirements for large-scale deployment include a fleet of aircraft with high payload capacity (to carry substances) powered by engines that can operate for long periods at high altitudes, and launch facilities located in both Northern and Southern hemispheres5 (assuming the deploying state wants to avoid disrupting tropical rainfall patterns).6 The aerospace and logistical resources necessary to meet these requirements are confined to a mere handful of states, including but not necessarily limited to the US, France, Germany, the United Kingdom (UK), Japan, Canada, Russia, China, India, and Brazil (see table below).4 These requirements exceed the economic, technical, and political capacities of non-state actors like companies and individuals.7
Aerospace companies capable of developing the technologies required for large-scale SAI deployment
| States | Major Aerospace Companies |
|---|---|
| US | Boeing, Lockheed, Northrup, General Electric, Pratt & Whitney, Gulfstream |
| France | Airbus (with Germany), Safran, Dassault |
| Germany | Airbus (with France), MTU |
| UK | Rolls-Royce |
| Japan | Ishikawajima-Harima Heavy Industries |
| Canada | Bombardier |
| Russia | United Engine Corporation, United Aircraft Corporation |
| China | Aviation Industry Corporation of China, COMAC |
| India | Hindustan Aeronautics Ltd. |
| Brazil | Embraer |
Large-scale unilateral deployment would also require sufficient economic, political, and even military resources to overcome opposition from other countries. In a future world dominated by the US and China, arguably only these two superpowers would be capable of withstanding pushback from others and deploying SRM at large scale on a unilateral basis.
Benefits, costs, and risks: the decision-making calculus
In a large-scale SRM scenario such as this, any country considering unilateral deployment – whether one of the states noted above or another – would face a mix of incentives and constraints. Presumably, the main motivation for undertaking a unilateral deployment would be to benefit from cooler temperatures and reduced climate risks. Such benefits, however, would by their nature take years to materialise, be shared with the entire world, and be subject to considerable uncertainty.
On the other side of the ledger, the constraints acting on a would-be unilateral deployer would consist of costs and risks. These might include the direct costs of SRM (in the tens of billions of dollars per year),8 economic (trade or financial) sanctions, and other penalties up to and including military strikes. Compared to the potential benefits, the costs of unilateralism would be immediate, concentrated on the deploying state, and more certain to inflict damage. Other risks would include heightened international tensions, greater geopolitical instability, and competing unilateral deployments.
From the point of view of a potentially deploying state, the long-term, diffuse, and uncertain benefits of large-scale SRM appear to be outweighed by short-term, focused, and definite costs and systemic risks. Every situation is different, and unilateral deployment is by no means impossible, but this suggests a rational decision-maker is unlikely to opt for unilateral deployment. Of course, decision-makers are not always fully rational. However, any leader contemplating sustained SRM will likely have come to consider it based on at least a rudimentary weighing of the costs and benefits.
Would countries really want to go it alone on SRM?
While the US or some other powerful country could go it alone and deploy SRM unilaterally, it is hard to imagine such an actor choosing to do so. Given the costs and potential for pushback, it is easier to imagine a powerful country that wanted to see SRM deployed forming a coalition with others or seeking a global agreement.
Thus, while unilateral deployment of SRM could happen, economic, technical, and geopolitical realities make this possibility less likely than is sometimes claimed. Only a small number of countries seem capable of implementing large-scale SAI and the incentives they would face point towards at least some form of cooperation with others.
Nevertheless, the risk that a country could deploy SRM alone or with a small coalition presents a challenge for the international community. Reducing this risk could involve strengthening existing barriers to unilateral deployment, for example, by institutionalising emerging norms against it through international legal instruments or political initiatives.9 Such governance might also involve creating new barriers, for instance, by coordinating and announcing a pre-planned multinational policy response to make clear the costs of rogue deployment if it occurs.
Open questions
- What specific tools and mechanisms could be established or enhanced to reduce the risk of unilateral deployment?
- Could there be ways to develop and deploy SRM not previously considered that might reduce barriers to entry and raise the risk of unilateral deployment?
- How will different national perspectives on SRM compare, and what will that mean for international cooperation?
Note: SRM as a “free driver” problem
The insufficient pace of emissions cuts has been characterised as a “free rider” problem. According to this framing, the benefits of cutting emissions will be shared globally and mostly go to future generations, but the costs will fall on those that act today. Consequently, present-day actors have reduced incentives to cut their own emissions and strong reasons to “free ride” on the efforts of other, more responsible actors. SRM, however, appears to pose the opposite problem: since the direct costs of SRM are low compared to the costs of decarbonisation (although SRM would not be free), whichever country wants the coolest temperatures has an incentive to set the global temperature where it likes. This could lead to a “free driver” dynamic in which the temperature is pushed below where most countries would prefer it by the country that wants it the coolest.10 Such an idealised model of country interactions, however, ignores the real-world constraints described in the rest of this article.
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Endnotes
- Rabitz F. (2016). Going Rogue? Scenarios for Unilateral Geoengineering. Futures 84A: 98-107. https://doi.org/10.1016/j.futures.2016.11.001
- “Minilateralism” is a variant of unilateralism in which small groups or “clubs” of countries implement SRM with a similar lack of regard for the rest of the world.
- Barrett S. (2008). The Incredible Economics of Geoengineering. Environmental and Resource Economics 39: 45-54. https://doi.org/10.1007/s10640-007-9174-8
- Horton JB, Smith W, Keith DW. (under review at Global Policy) Who Could Deploy Stratospheric Aerosol Injection? The US, China, and Large-Scale, Rapid Planetary Cooling. Preprint available at https://media.rff.org/documents/HORTON_paper2.pdf
- Janssens M, de Vries IE, Hulshoff SJ. (2020). A Specialized Delivery System for Stratospheric Aerosols: Design and Operation. Climatic Change 162: 67-85. https://doi.org/10.1007/s10584-020-02740-3
- A robust finding of climate model simulations is that if SAI (or any other type of SRM) is restricted to only one hemisphere, then the tropical rain belt will move away from the cooler hemisphere. This could result in very large changes in tropical rainfall, with large reductions in rainfall in the tropics of the cooler hemisphere, and large increases in the warmer hemisphere.11
- Hartley K. (2014). The Political Economy of Aerospace Industries: A Key Driver of Growth and International Competitiveness? Cheltenham, UK: Edward Elgar. https://doi.org/10.4337/9781782544968
- Smith W. (2020). The Cost of Stratospheric Aerosol Injection Through 2100. Environmental Research Letters 15: 114004. https://doi.org/10.1088/1748-9326/aba7e7
- Eliason A. (2021). Avoiding Moonraker: Averting Unilateral Geoengineering Efforts. U. Pa. J. Int’l L. 43:429. Available at: https://scholarship.law.upenn.edu/jil/vol43/iss2/3
- Weitzman ML. (2015). A Voting Architecture for the Governance of Free-Driver Externalities, with Application to Geoengineering. Scandinavian Journal of Economics 117: 1049-1068. https://doi.org/10.1111/sjoe.12120
- Haywood JM, Jones A, Bellouin N, et al. (2013). Asymmetric forcing from stratospheric aerosols impacts Sahelian rainfall. Nature Climate Change. 3(7):660-5. https://doi.org/10.1038/nclimate1857
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