go to top
The sun shines near the Space Needle during a record-setting heat wave, Seattle, Washington, June 2021. The sun shines near the Space Needle during a record-setting heat wave, Seattle, Washington, June 28, 2021 (AP photo by Ted S. Warren).

Reflecting Sunlight to Reduce Climate Risk

Monday, Oct. 25, 2021

The slow pace of carbon emissions reductions and the increasingly obvious, devastating consequences of climate change make it imperative for the world’s governments to develop a broad portfolio of strategies to manage climate risk. That portfolio currently includes three main strategies, all of which will be discussed at the upcoming United Nations Climate Change Conference in Glasgow: mitigation of the causes of climate change, via emissions cuts; adaptation to its effects; and carbon dioxide removal, via both nature-based solutions and negative-emissions technologies

Given the quickening pace and growing magnitude of the climate emergency, however, the world must also consider the feasibility and wisdom of adding a fourth arrow to this quiver: solar climate intervention, or SCI. Also known as solar radiation management, solar geoengineering or albedo modification, SCI refers to large-scale efforts to counteract the warming effect caused by accumulating greenhouse gas emissions, particularly by enhancing Earth’s reflectiveness through experimental techniques such as dispersing aerosols in the stratosphere or brightening marine clouds with salt crystals

SCI has been proposed as a relatively inexpensive and fast-acting strategy to slow or even reverse climate change and its consequences while humanity makes progress on emissions reductions and carbon-dioxide removal. It will surely become more tempting as the world blows well past the Paris Agreement targets and planetary temperatures rise. At the same time, considerable scientific uncertainty surrounds the potential efficacy and impacts of such interventions, and there are few international rules governing the intentional manipulation of the Earth’s climate system. 

This situation is untenable. Governments need a better understanding of the potential risks, opportunities, costs and benefits of the relevant technologies, in order to make informed and responsible decisions regarding their use. They also need a global governance framework to reduce the dangers of uncoordinated, unilateral approaches to their deployment. To fill these gaps, national authorities must promote and expand collaborative scientific research on methods to reflect sunlight, while also formulating standards, principles, norms and rules regarding the use—or non-use—of SCI. The time to lay the foundation for international cooperation is now, when such methods remain in their infancy.

Critics have raised a host of practical and ethical objections to SCI, an undertaking that can admittedly sound very creepy. These include fears that it could reduce the urgency of mitigation efforts—the so-called moral hazard argument; lack political legitimacy and democratic accountability; threaten human health and safety; disrupt the planetary environment, with impacts on precipitation patterns, biodiversity and ecosystems; harm agricultural productivity; and exacerbate diplomatic tensions and geopolitical rivalries, among others. There are also concerns it could violate principles of procedural, distributional and intergenerational justice, by permitting select countries to set the global thermostat, benefitting some populations and regions at others’ expense, and consigning our descendants to geoengineering schemes in perpetuity. 

Policymakers urgently need more accurate information about whether SCI is feasible and, if so, what impacts it is likely to have on both the natural and human worlds.

Some critics object to even research into SCI, fearing that slippery slope and “socio-technical lock-in” dynamics will inevitably lead to its deployment. Many—though hardly all—environmental advocates seek to avoid normalizing the enterprise. Combined, these concerns help explain the reticence of many governments to explore the technology further. 

These potential perils deserve to be assessed seriously. But they need to be evaluated and weighed not in isolation, but alongside the known dangers, risks, tensions and inequities inherent in the experiment that humanity is already running by pumping massive quantities of greenhouse gases into the atmosphere. The relevant question is: How do the anticipated risks of climate change compare to the risks of climate change plus sunlight reflection? To answer this question, we need more and better insights from social as well as natural science.

It is important for social scientists, in particular, to scrutinize common critiques of SCI rather than taking them at face value. Consider the “moral hazard” and “slippery slope” arguments. The former asserts that SCI will inevitably displace mitigation efforts, by giving humanity—and especially fossil fuel companies—an apparent free pass to continue polluting. The latter contends that any research in this field will invariably lead to deployment. In fact, there is little empirical evidence to support either claim. Indeed, some survey results suggest that SCI could actually increase public support for reducing emissions, by underscoring the gravity of the climate crisis. Likewise, basic research and limited field experiments could well result in political authorities deciding not to attempt sunlight reflection. 

What policymakers urgently need is more accurate information about whether SCI is feasible and, if so, what impacts it is likely to have on both the natural and human worlds. Unfortunately, current budgets for SCI research are negligible, a minute fraction of what the world invests on the rest of its climate risk-management portfolio. In April 2021, the U.S. National Academies of Science, Engineering and Medicine released a landmark report, “Reflecting Sunlight,” advocating increased U.S. funding in this area. The Biden administration and the U.S. Congress should take that advice, expanding support for relevant atmospheric research in the Department of Energy and the National Oceanic and Atmospheric Administration, or NOAA. 

To build international trust, however, any major U.S. or broader Western research effort on SCI must simultaneously be part of a global one, involving scientists in both developed and developing countries in one common enterprise. The pioneering work of the Solar Radiation Management Governance Initiative, a globe-spanning network that seeks to build capacity for SCI science in the developing world, where the impacts of climate change are likely to be especially harsh, provides one platform on which to build. The United States and other major governments should support multilateral cooperation to improve technical knowledge and scientific assessment of SCI and its impacts, particularly within the framework of the Intergovernmental Panel on Climate Change, which has already commenced modest work in this field, as well as other technical bodies, like the World Meteorological Organization. They should also examine the track record of successful multilateral cooperation on scientific mega-projects, like the International Space Station, as potential models.  

When it comes to the question of SCI governance, it is important to distinguish between what is required for research versus actual deployment. Some diehard skeptics of SCI insist that even basic research must be subjected to stringent national and global governance requirements. They advocate creating bespoke mechanisms specifically for this purpose, as well as mandating onerous public consultation. While transparency, information-sharing and accountability are important, raising these hurdles too high could strangle basic research that poses infinitesimal risks to human health and safety but is urgently needed in the face of the quickening climate catastrophe. Where national agencies with a mandate to approve and regulate atmospheric research already exist, as with the Department of Energy and NOAA in the U.S., it makes little sense to create brand new mechanisms. Similarly, while public comments and consultations are important to build trust, the primary locus of democratic accountability and oversight should remain the people’s elected representatives, including, in the U.S. case, Congress. 

Even as they promote collaborative research, national governments should engage in multilateral discussions on the desirability of any future deployment and on the standards, rules and procedures that should govern such decisions. Choosing the appropriate mixture of international venues will be critical to success. In the interest of legitimacy and buy-in, the United States and other major countries should support expanded discussions on SCI within universal-membership bodies like the U.N. General Assembly, the U.N. Environment Assembly and the U.N. Framework Convention on Climate Change, or UNFCCC, negotiating process. They might also urge the U.N. secretary-general to appoint a high-level global commission to draft an international code of conduct for large-scale research and deployment, which could inform any eventual international convention. 

However, given the susceptibility of universal forums to political paralysis, ideological division and lowest-common denominator outcomes, the world’s major powers may also want to elevate discussions on SCI governance to the U.N. Security Council, an authoritative body that can make decisions that are binding on all U.N. member states, as well as more flexible, “minilateral” forums like the G-7, G-20 or even tailor-made coalitions of the capable, interested and—ideally—like-minded. The focus of such efforts would be to encourage both mutual restraint in deployment and collaboration in research activities. 

To some, SCI might seem like the opening scene of a dystopian sci-fi movie. To others, it is the technological breakthrough at movie’s end that saves humanity from extinction. But without more research and a framework for whether and how to implement it, we won’t know which timeline we’re actually in.

Stewart Patrick is the James H. Binger senior fellow at the Council on Foreign Relations and author of “The Sovereignty Wars: Reconciling America with the World” (Brookings Press: 2018). His weekly WPR column appears every Monday.

To read more,

enter your email address then choose one of the three options below.

Subscribe to World Politics Review and you'll receive instant access to 10,000+ articles in the World Politics Review Library, along with new comprehensive analysis every weekday . . . written by leading topic experts.