Skip to main content

Governance is Essential to Manage the Risks of Solar Radiation Modification

Senior policymakers everywhere tend to react to the idea of new climate-altering technologies in a similar way: with a mix of curiosity, potential hope, and palpable anxiety.

It’s a natural reaction, especially in these deeply challenging times.

For the past three years, my colleagues and I from the Carnegie Climate Governance Initiative (C2G) have been meeting with senior interlocutors around the world, both in and out of government, and alerting them to the critical need for multilateral governance of powerful but risky new ideas to reduce the impacts of climate change.

These include proposals to remove billions of tonnes of CO2 already in the atmosphere, and technologies to reflect back sunlight to lower the global temperature, known as solar radiation modification.  

All pose profound governance challenges, which need to be addressed. The latter, if deployed at a global scale, would affect every country on Earth.

In response, we are regularly asked the same questions. What are the risks and possible benefits? Are they a substitute—or a dangerous diversion—from the urgent need to reduce CO2 emissions? Are there any existing international laws or bodies to govern them?

And last but not least, why are we drawing attention to this issue now, when agendas are packed and there are other competing priorities?

Having worked for eight years in former UN Secretary-General Ban Ki-moon’s climate change team, I am familiar with these kinds of concerns.

For many senior policymakers, this is the first time they’ve had a conversation about emerging climate technologies, a topic that raises profoundly difficult questions about risk management, ethics, international security, and sustainable development.

But the consequences of our present course are also extremely serious. Despite a temporary drop in CO2 emissions during the pandemic, scientists say we must reduce global emissions to net zero and then net negative if the world is to meet the Paris goal of limiting temperature rise to 1.5°- 2°C above pre-industrial levels by 2100.

How can the world reduce climate risks in a way that is safe, inclusive, and fair? And what role can governance play in reducing the specific risks posed by solar radiation modification, were it ever to be used? This is a new type of challenge, and it’s not clear we are ready to meet it.

What Are Emerging Climate-Altering Technologies?

Any discussion of technologies that would intentionally alter the climate must begin with a recognition that our “business as usual” emissions pathway leads to disaster. National pledges made thus far under the Paris Agreement fall significantly short of what is needed.

While the long-term consequences of COVID-19 are unclear, the world appears to be hurtling toward a catastrophic 3-4°C temperature rise by 2100—twice the level set by the Paris Agreement. This would mark the end of civilization as we know it within eighty years, easily the lifespan of someone born today. Seen from any angle—environmental, economic, geopolitical—climate change could have destructive global impacts far greater than the current pandemic.

It is in this context that some scientists, business, and policymakers have begun exploring a range of new approaches and technologies to supplement existing climate response tools. These include nature-based approaches, such as enhancing soil carbon content or restoring forest ecosystems to remove excess CO2 from the atmosphere and store it, as well as technical methods that would directly capture CO2 from ambient air. Removal approaches vary considerably in their potential, readiness, permanence, cost, and risks of negative side-effects. Their specific governance challenges vary as well.

Solar radiation modification[1] is perhaps the most controversial of these emerging technologies. It has the potential to provide quick, tangible benefits, but it also poses potentially serious risks. It includes ideas that would intentionally alter the climate by creating brighter clouds at sea or spraying reflective particles into the stratosphere.

These technologies would not address the anthropogenic causes of climate change, but rather address a key symptom of climate change—temperature rise—by reflecting sunlight into space to rapidly cool the planet.

One particular technology—stratospheric aerosol injection—could potentially reduce global temperatures very quickly (within months), according to computer models, potentially providing significant human health benefits and other indirect gains, at a limited operational cost.

No other approach or technology we know of can do this. This makes it potentially very attractive to politicians seeking to buy more time to reduce emissions or show quick results to their constituents.

However, solar radiation modification would not be a substitute for traditional mitigation or large-scale removals, only a potential supplement. And the risks of stratospheric aerosol injection could be very high, not only for the environment, but for geopolitical stability, equity, and attainment of the Sustainable Development Goals.

Why Governance and Why Now?

Perhaps the greatest risk concerns governance—or rather, the present lack thereof.

Governance is about far more than governments, rules, and regulations. It requires interlocutors from across all sectors of society, both the powerful and the marginalized, coming together to discuss, learn, share knowledge, and take decisions at multiple levels. And it must include those most affected by climate change—including those who would be most impacted by any potential use of solar radiation modification. Governance also embraces deep ethical issues regarding legitimacy, decision-making authority, and inter-generational equity, among others.

There are currently no comprehensive international governance frameworks for solar radiation modification. Until recently, discussions about these emerging technologies have been limited to a small community of scientists.

In fact, the vast majority of policymakers, and their advisors, around the world do not know enough about these technologies to be aware of their challenges, including why they need to be governed. This poses unacceptable risks to current and future generations. 

Some believe that talking about these technologies may reduce incentive for the urgent and essential task of reducing global emissions, thus creating a “moral hazard.” While this is a valid concern, C2G believes the greater risk is in ignoring or postponing a discussion about technologies such as solar radiation modification. We do not have the luxury of time.

The COVID-19 crisis has made it abundantly clear that when it comes to global challenges, there is a very high cost to waiting—waiting to prepare, to mobilize key actors, and to develop governance at multiple levels to mitigate risks.

In short, the longer the world delays sorting out how to govern technologies that would intentionally alter our climate, the more we will all pay in terms of increased risks.

The time to anticipate risks and develop governance is now, before some actor—state or non-state—unilaterally decides to deploy solar radiation modification technologies that have global impacts. By any measure, this is a timely investment in a safer future.

Laying a Foundation for Governance

C2G, a foundation-funded initiative, was created in 2017 to help minimize these risks by catalyzing governance conversations with global policymakers and their advisors, as well as with non-state actors. This mission—to catalyze the creation of effective governance for climate altering technologies—is unique.

Over the past few years, C2G has broadened the conversation on climate-altering technologies from the academic and research community to the policy world. It does not aim to determine the outcome of these discussions or provide answers. Rather, C2G takes a broad, risk management approach. In a rapidly warming world, C2G encourages policymakers to consider both the risks of action—and inaction—with respect to any potential climate intervention.

Its role is to ask critical questions, and to catalyze inclusive and well-informed discussions in order to fill governance gaps, both nationally and globally. C2G is impartial regarding the potential use of any proposed climate-altering technologies or interventions. These are choices for society to make.

But make them they must—and soon.

In March 2020, Australian scientists, funded by the government, conducted an outdoor experiment aimed at protecting the Great Barrier Reef using marine cloud brightening—a form of solar radiation modification—governed under existing domestic laws.

A different outdoor experiment in the United States is under discussion, potentially paving the way for further development of stratospheric aerosol injection.

As climate impacts continue to worsen, there will be increased pressure on governments in both developed and developing countries to use additional tools beyond traditional mitigation.

Three Common Concerns from Policymakers

Since its inception, C2G has met with senior policymakers in scores of governments around the world. It has also met with senior officials across the UN system, and dozens of civil society organizations and faith groups. Much more learning is needed about the risks and potential benefits of these technologies—known and unknown—as weighed against the dangers of a warming world.

Overall, C2G’s message is clear: Difficult choices lie ahead. There are no risk-free options to address the climate crisis; every course of action has costs and trade-offs as well as potential benefits.

The risk of the world’s present course is simple: Society-wide transformational changes to decarbonize the global economy are urgently needed. But the speed and scale of action we see thus far falls far short. And the current leadership of the world’s largest emitting countries does not invite optimism.

At the same time, new ideas to tackle our crisis bring major risks of their own. To that end, governance for solar radiation modification should be developed as soon as possible and set within the context of an overall climate response.

In our conversations with global policymakers, we sense a growing recognition of the need for a robust science-society-policy dialogue, starting now. We also hear three common concerns:

1. Decision-making authority: Whose finger is on the global thermostat? Who decides to use—or not use—technologies with planetary impacts? On what basis, and under what process?

This goes to the heart of legitimacy and decision-making authority in a multilateral system already under great strain.  

At present, there is no clear answer to these questions under existing international law. There is no existing institution uniquely equipped to address all the governance challenges raised by stratospheric aerosol injection. Nor is there currently an appetite for creating new institutions. Some have argued that a polycentric approach might serve best under present circumstances.

2. Linkages with other issues: How would solar radiation modification affect the Sustainable Development Goals (SDGs)? Much more research is needed, but clearly there could be significant impacts—both positive and negative—on health, food, water security, and biodiversity.

Another concern is solar radiation modification and its implications for global security. Some of the impacts of stratospheric aerosol injection could create global winners and losers (or be perceived to do so), thus potentially triggering conflicts. Ungoverned deployment of this technology could cause serious geopolitical instability without a multilateral mechanism for deciding if and when the technology were ever to be used. Regional use of marine cloud brightening could also provoke regional and/or international tensions.

3. The public’s response: As with other controversial technologies (GMOs, stem cell research, cloning), solar radiation modification raises profound questions about humanity’s relationship to nature, to the divine, and to future generations.

With more than 80 percent of the global population professing adherence to a religion, faith communities and ethical leaders could have a major influence on the public’s response to emerging climate technologies—and hence their governance. To be seen as legitimate, the governance of solar radiation modification will need to address deeply rooted values and beliefs about justice, equity, and inclusivity, among others.

Are we foolishly “playing God,” as some have said? Do we have the right to deliberately alter the one atmosphere we all share? How can young people have a say in these matters? After all, their generation—and future generations—will live with the consequences.

Others argue that solar radiation modification could rapidly reduce temperatures, thus benefitting some of the world’s poorest and most vulnerable communities who are located in areas already suffering from extreme heat under today’s 1.1°C rise in global temperatures. Imagine the grave consequences of a “business as usual” emissions pathway, where temperatures are anticipated to rise to an estimated 3°C or 4°C by century’s end. Significant swathes of the Earth might simply be uninhabitable for hundreds of millions of people.

Why Act Now?

Society will need to make difficult decisions in the next decade on how to respond to the climate crisis. This includes weighing the possible risks and benefits (known and unknown) of any potential use of solar radiation modification against those of a rapidly heating planet, whose environmental degradation is accelerating due to human influence.

Policymakers still have a window of opportunity to proactively lead a global conversation about these technologies, and to build multilateral frameworks to govern them, before one or more countries or non-state actors act unilaterally.

Given its global nature, governance of solar radiation modification will require global arrangements in the United Nations, building on actions and agreements in regional and global intergovernmental processes, including, inter alia, the European Union, the African Union, the G7, and the G20.

As COVID-19 has reminded us, governance that anticipates a crisis, instead of merely reacting to one, can save lives. A second lesson is also true: We ignore science at our own peril. Humanity’s oversized imprint on the climate and ecosystems will continue to have serious consequences, affecting not only sustainable development, but also global peace and security.

And yet, while science must be the evidence base for decision-making, ethics and values are at the heart of how these emerging technologies will be viewed by the public. Credible, impartial information and open dialogue are essential for building trust.

There remains a great deal of learning and outreach ahead. Nonetheless, the doors to serious global conversations about the governance of these powerful technologies have been opened.

The issues C2G is raising are difficult and uncomfortable. But we have found that by the end of our conversations, despite any initial hesitation, our interlocutors tend to agree: The greatest risk lies not in broaching contentious topics, but in not being prepared to face them, openly, honestly, and with humility.


Carnegie Council for Ethics in International Affairs

[1] C2G does not use the word “geoengineering” as it encompasses a wide variety of technologies and approaches that pose very different challenges. This can confuse, instead of contribute, to their effective governance and impede constructive discussions with policymakers. “Geoengineering” also contains an implicit assumption that it is possible to engineer the climate, which may underplay the complexity of the Earth system. Please see our blog on “what’s in a name.”

About the Author

Cynthia Scharf

Senior Strategy Director, Carnegie Climate Governance Initiative
Read More

Environmental Change and Security Program

The Environmental Change and Security Program (ECSP) explores the connections between environmental change, health, and population dynamics and their links to conflict, human insecurity, and foreign policy.  Read more

Global Risk and Resilience Program

The Global Risk and Resilience Program (GRRP) seeks to support the development of inclusive, resilient networks in local communities facing global change. By providing a platform for sharing lessons, mapping knowledge, and linking people and ideas, GRRP and its affiliated programs empower policymakers, practitioners, and community members to participate in the global dialogue on sustainability and resilience. Empowered communities are better able to develop flexible, diverse, and equitable networks of resilience that can improve their health, preserve their natural resources, and build peace between people in a changing world.  Read more