There is no question that the top priority in combating climate change is quickly mobilizing the policies and investments needed to dramatically reduce greenhouse gas emissions. Yet, as these efforts lag and as climate impacts escalate, there is also a growing need to seriously consider additional options, including different forms of direct intervention in the climate (sometimes referred to as “geoengineering”).
Much attention has focused recently on direct air capture—the use of technologies to draw carbon from the atmosphere. Such approaches may indeed prove critical by mid-century to achieve a net zero balance between emissions and withdrawals. But a different set of approaches known as solar climate intervention (SCI) could, in addition, offer the option of a rapid response to avoid dangerous or abrupt climate change.
SCI encompasses a range of techniques that effectively increase the reflection of sunlight from the atmosphere as a means of slowing the Earth’s warming. While there are several emerging research efforts around the world, there is as yet no international body looking comprehensively at these options. This is concerning because it may impede progress in understanding their risks and potential, and because it may increase the risk that individual nations move forward on their own.
To help inform this critical debate, C2ES and SilverLining today published a paper by international environmental law experts Sue Biniaz and Dan Bodansky assessing the ability of existing international bodies to evaluate and, potentially, govern SCI.
The paper opens with a challenging reality: the international response to climate change has been, and may continue to be, inadequate to ensure a safe global climate. Even if all the countries of the world undertake aggressive mitigation immediately, it might not be possible to avoid changes in natural systems that accelerate climate change beyond our ability to counter it.
Again, rapidly reducing carbon emissions is the highest priority for stabilizing the climate and sustaining natural systems over time. But as climate change increasingly puts near-term safety and major natural systems at risk, it is important to consider how we can facilitate a coordinated global approach to assessing possible interventions and supporting cooperative, science-based decision-making about their potential use.
Potential SCI techniques include dispersing particles in the stratosphere that scatter sunlight (stratospheric aerosol injection), increasing the reflectivity of marine clouds with saltwater spray (marine cloud brightening), and inducing precipitation in upper atmospheric clouds to release more reflected sunlight (cirrus cloud thinning). Because SCI is believed to be one of the few ways to cool the planet quickly, it could play a particularly important role in addressing climate tipping points, where rapid action could be required.
Whatever their promise, these ideas also pose significant, uncertain risks. That’s why it is paramount that decision-making related to solar climate intervention considers the “two safeties” outlined by Biniaz and Bodansky—both the safety of the global climate and the safety of the potential use of climate intervention. This would provide a strong foundation from which the international community can approach SCI cooperatively and scientifically.
It’s worth noting that this type of risk assessment requires considerable research. Today, there is just over $10 million per year available globally for research on rapid atmospheric climate interventions. In the United States, funding for broad climate research comprises less than 0.2% of federal spending. The recent majority staff report of the House Select Committee on the Climate Crisis calls for additional research funding for atmospheric (solar) climate intervention, an indication of growing support.
Biniaz and Bodansky consider a scenario in which a group of countries seeks an approach that is both cooperative and informed by science, and identify two critical roles at the international level: first, producing comprehensive expert assessments of the available scientific and technological research; and, second, international decision-making based on such assessments on whether and under what conditions to use one or more SCI technologies
Surveying the landscape of existing international forums, the authors conclude that there is no single body that is ideally suited to serve both functions.
There are forums with relevant capabilities, particularly with respect to scientific assessment. For instance, a special report by the Intergovernmental Panel on Climate Change on climate tipping points could provide robust scientific assessment of potential rapid responses, including SCI. In terms of decision-making, the UN Security Council may be uniquely placed given its broad mandate and ability to act quickly but its limited membership might be perceived as a liability.
While the paper was limited to surveying existing institutions and did not consider the option of creating a new, ad hoc forum or process, specifically designed to address SCI, it is possible that a new forum may be an effective way to achieve these goals, though the time and execution risks would likely be substantial. It is vital that governments and stakeholders begin thinking now about the options, and the research required to inform them, so that, should the time come, the international community is prepared to carefully assess whether SCI should play a role in averting dangerous climate change.