Our planet is like a greenhouse. That’s what children are taught when we first introduce the concept of climate change in classrooms. Teachers use this to explain why their generation stands on the brink of environmental devastation. Solar radiation goes in, but only some of it goes back out—the rest gets trapped inside the greenhouse and causes the planet to get hotter. At this stage, even a child can raise their hand and ask, “Then, why can’t we just stop the sunlight from coming in?” That’s solar geoengineering in a nutshell. From building giant sun shields that orbit the planet or spraying sea salt into marine clouds so they become more reflective, geoengineering tries to tip the balance of solar radiation inside the greenhouse. 

Geoengineering, otherwise known as climate intervention, is the intentional large-scale manipulation of the Earth’s climate. Is it a dangerous techno-utopian fantasy, or a last resort to protect the most vulnerable? It depends on who you ask. What’s inarguable is that something big has to be done: the world is getting warm very, very quickly. The Intergovernmental Panel on Climate Change’s (IPCC) 2018 report cautioned world leaders to limit warming to 1.5°C and recommended reasonable policy pathways to cut 45 percent of emissions by 2030. These suggestions included using renewable energies and bio-based feedstock (such as chemicals made from agricultural crop waste) to supply the world’s growing energy needs—hardly a radical deviation from the current corporate-approved path. But, of course, if business continues as usual, our world is on track to hurtle past 2.5°C of warming above pre-industrial levels. Since the publishing of the 2018 IPCC report, the world has pumped over 70 billion metric tons of carbon dioxide into the atmosphere from the burning of fossil fuels and industrial activities. Even in optimistic scenarios where the world takes drastic actions to cut emissions to net-zero by 2050, impacts from the warming caused by residual greenhouse gases will still be substantial enough to cause huge devastation to vulnerable communities.

Geoengineering, however, aims to mitigate the effects of anthropogenic climate change. Though it can take many complex forms, the subset known as solar radiation management (SRM) would have the largest net global impact on cooling. In whatever form it takes, SRM involves reflecting a small portion of inbound sunlight away from the surface of the Earth. Ideas on how to achieve that range from stupid (giant space mirrors) to more thought-provoking (cloud thinning). But probably the most promising form would be chemical aerosols—suspended particles that are injected into the atmosphere to help diffuse downward solar radiation. Historical volcanic eruptions have given scientists the opportunity to study the effect of sulfate aerosols in particular. For example, in 1883, the Krakatau explosion caused global air temperatures to drop by as much as 2.2°F (1.2°C) and the temperature did not return back to normal until 1888.

The concept of weather modification has existed since the Cold War, when geoengineering was researched as a weapon. Between 1967-1972, Operation Popeye saw 2600 aircraft flying over Vietnam, carrying chemicals such as silver iodide. These chemicals can trigger rainfall and the U.S. hoped that prolonging Vietnam’s monsoon season would obstruct the Viet Cong’s movements. The ethical issues of such practices are outstanding. Climate modification, when used as a weapon, was not targeted. Muddying the roads and flooding the supply lines the Viet Cong used also meant doing the same to civilian populations in the area. The US military also came under fire for allegations that they caused terrible floods in North Vietnam (though they rejected that any rainmaking operations took place during those specific time periods).

But given the stakes of the moment, it can be argued that the technology’s unsavory past shouldn’t tarnish its present. By lowering peak global temperatures, scientists could potentially save millions of lives that would otherwise be lost to extreme weather events and their secondary impacts such as disease, famine, and droughts. There is high scientific confidence that reducing insolation (i.e. exposure to the sun’s rays) through stratospheric sulfates would reduce peak temperature rises.

However, even during its current infancy, geoengineering is not everyone’s darling. Climate intervention has faced intense resistance from many parties, some informed by predictions that geoengineering may actually exacerbate environmental hazards in some regions of the world. Professor Alan Robock, Distinguished Professor in the Department of Environmental Sciences at Rutgers University, has been a long-standing skeptic about the net utility of depositing sulfur into the atmosphere to control warming. In an interview with Current Affairs, he said, “It would cool the Earth and it would reduce some of the impacts of global warming, but it would also produce a lot of risks that could reduce precipitation, or could destroy the ozone layer and let ultraviolet radiation through.”

Scientists such as Robock study nature’s closest parallel to what climate interventionists are proposing: those large volcanic eruptions, which can deposit upward of 400,000 tons of sulfur dioxide into the stratosphere. Depending on the location, height, and size of the eruption, Robock concludes that changes in atmospheric circulation—large-scale movements of air in the Earth’s atmosphere—may actually produce even more heating in some regions and reduced rain in others. So, the specifics of where these negative impacts are localized depend on the deployment of SRM and also whether we continue to be reckless with greenhouse gas emissions. We’re hungry for climate solutions, but pumping aerosols in the atmosphere might make us into a snake that eats its own tail.

Sulfur dioxide in the stratosphere may also react with the ozone in the atmosphere, as well as with chlorine from chlorofluorocarbons (CFCs) that were once used in refrigerants. These reactions would further deplete the ozone layer and would allow for more harmful levels of UV-B rays to reach Earth’s surface. This could cause damage to our health, food security, and natural ecosystems, possibly in ways we can’t yet fully predict or imagine. 

The risks of geoengineering are substantial, but risks are inherent to new technologies, says climate scientist Professor David Keith. He’s a professor of applied physics at the Harvard School of Engineering and Applied Sciences, as well as a part of the university’s SCoPEx experiment, which aims to measure air-aerosol-radiation interactions outside of the laboratory. In our interviews, he regularly uses the analogy of some mRNA vaccine technologies which can be used to create bioweapons, “Nobody’s suggesting we shouldn’t make the vaccines. We’re just suggesting we should regulate bioweapons.” In that same way, though the risks of exploitation exist for geoengineering, they have to be weighed against potential benefits.

“Is it possible that the technology could be used for great harm? Yes, but that is true of almost any technology in the modern world,” Keith says. 

Any technology could be used for harm, sure, but those harms are not always equal. Geoengineering may save some lives and destroy others. And decisions about who accrues environmental risks—e.g., whose homes might be flooded and who might find themselves without clean water—have generally been managed by the people at the very top of society, who might not have the entirety of humanity’s best interests at heart. So, how do we honestly weigh the risks of geoengineering? Whose risks are they, and how bad could they be?

Fighting for the Thermostat

Robock says that in a conference he attended ten years ago, Princeton professor Robert Socolow took a poll which asked what the worst possible outcome of stratospheric geoengineering could be. The results? Global nuclear war. 

Different parties have different ideal temperatures, just like a feuding couple. Rather than fighting over blankets, however, countries have large-scale conflicting interests when it comes to the global geoengineering agenda. For example, countries that are at risk of sea-level rise like Indonesia might want to turn the temperatures way down. Countries used to bitter winters, such as Russia, might enjoy slightly warmer weather. Resulting “climate wars” could arise as states struggle against each other to determine the deployment of geoengineering—especially who gets to aggregate the most benefits and who is forced to aggregate the most risk. In a scenario where there are likely to be winners and losers, the governance of such a technology becomes dicey.

Though it is relatively inexpensive to inject aerosols into the atmosphere, solitary action may not lower global temperatures to a significant degree. Most experts agree that geoengineering would have to be a multilateral or international effort. Coordination could, in theory, be arranged by an internationally-respected body like the United Nations. But even in organizations like the U.N., influence over policy is still asymmetrically distributed, especially when it comes to the political and economic capital to leverage mechanisms like aid or international trade. And unfortunately, countries that monopolize such power also tend to be located in the same hemisphere—the Global North, with very few of them having low-lying territories in the tropics. Many states in the Global North share the same optimal temperature range, weakening the possibility that similarly powerful states could act as counterbalancing geopolitical forces.

Especially when risks of lowered precipitation rates may aggregate along the equator, disadvantages to the already climate-vulnerable may not be represented by eventual deployment policies. Countries like India, for example, are vulnerable to droughts. In 2015 peninsular India was struck by a flash drought, which impacted its widespread crop production. It may even be the case that no matter what policy is undertaken, even if it is one that minimizes risks to all parties, negative weather impacts such as droughts or cyclones might still result. In that scenario, who’s accountable? In our interview, Robock said, “In general, there’s not a good record of taking care of people that are disadvantaged by government action.” Just ask the millions of people who become environmental refugees annually, such as the 50,000 people who were displaced into Bangladesh’s city slums due to floods last year. Robock notes further that establishing causality between a specific weather event and geoengineering policy can be exceptionally difficult, and hence would confuse any attempt to hold parties liable for compensation. 

One of the groups most vehemently opposed to geoengineering is the environmental ETC Group, of which Silvia Ribeiro is the Latin America Director. She asks, “Where is the governance that can control such a powerful technology, especially considering we cannot govern climate change today?” Given that most governments have so far shown either a gross incompetence or an unwillingness to decisively and collectively act to mitigate climate change, Ribeiro sees no difference in the future of geoengineering. 

She also points to the risk of termination—that key states may abruptly choose to halt their participation in geoengineering and destabilize the global climate. For example, it’s likely that wealthier Western states may foot most of the cost of geoengineering (e.g., the sulphur and the high-tech, high-altitude planes needed to deposit it). In turn, some administrations may grow resentful at having to pay the bill while other countries get to free-ride geoengineering’s benefits. This termination risk may cause temperatures to rebound at astonishing rates to the levels they would have reached without geoengineering.

However, Keith and other climate scientists like Peter Irvine from University College London point that there are very obvious checks and balances to such risks. States have a shared vested interest to not recklessly terminate their geoengineering precisely because sharp rises in temperature would be to everyone’s detriment. Similarly, undertaking action as a single hemisphere may accrue very few benefits without the cooperation of the Global South. Those benefits would then be outweighed by the huge international backlash from those negatively affected, taking such forms as sanctions or condemnation. 

“I agree with the kind of position that says that if the West did have a way to just use geoengineering to just make themselves better off and screw the poor, they’d probably do it,” Keith says, “but geoengineering is a technology that is relatively hard to exploit compared to other technologies.” And unlike vaccines, the benefits of solar geoengineering would accumulate more rapidly to the poor by decreasing peak temperature rises—a tide that lifts all boats rather than a resource that can be hoarded.

But political realities may be a lot messier than the scenarios presented so far. States could arrive at an optimal geoengineering scenario which properly balances all states’ interests, but as long as states could have benefited more from a competing strategy, a different administration may choose to selfishly veer off course. Factors such as this (and the distortions introduced by geopolitical tensions) create inconsistencies in policy. For instance, conflicts between states may lead to an overall reduction in cooperative behavior, even if such conflicts are clearly harmful to all parties involved. The nuclear stand-off between the U.S. and Soviet Union comes to mind. Yes, it was always in both actors’ rational self-interests to avoid existential threats. However, the geopolitical optics of being the first to concede and de-escalate the nuclear arms race meant that both inched closer to Armageddon. 

Usually, inconsistencies in policy deployment are to be expected—but here the game seems risky. A small fractional change in precipitation patterns could, for example, devastate crop yields or displace entire communities. Who then answers to these damages?

Moral outrage for who?

Though the ethical harms of pursuing geoengineering have been explored, the implications of the counterfactual are often left out. The potential of droughts or lowered precipitation does have to be weighed against the climate-induced events—like extreme hurricanes and month-long bushfires—that will definitely result from global warming. The effects of geoengineering are still theoretical, but we know that climate change already exacerbates pre-existing inequalities.

Imagine a graph of where global temperatures peak—3° in Poor Country X, 1° in Rich Country Y, and so on. Shaving a bit off the top may be a key step toward reducing inter-country income inequality. If geoengineering does turn out to be a tool whose comparative benefits outweigh its harms, proponents argue that the choice not to deploy it would be negligence. 

However, there is no consensus among the scientific community about the risk trade-offs of geoengineering. In March, the U.S. National Academy of Science released a report that recommended a $100-$200 million research budget to better understand the mechanisms of geoengineering. “So, people are working on it and some people still think it’s a good idea,” Robock says, “But I think there are some risks [like ozone depletion and rapid warming if deployment ends] that are showstoppers that you’ll never be able to solve.”

Alongside geoengineering’s potential physical hazards, many worry that climate intervention is just a convenient excuse for the world’s dirtiest polluters. As Ribeiro from the ETC Group highlights, “All the investment in geoengineering comes from [the U.S.] that historically and presently is the largest consumer of energy per capita in the world.” Suspicious of what this entails, she and other commentators predict that SRM presents a moral hazard—a way for polluters to keep burning fossil fuels if all the symptoms can be technologically managed. 

But who is this pearl-clutching and hand-wringing for? Despite the constant concern about how geoengineering may impact the most disenfranchised, not much research is present about what the public in the Global South actually thinks about it. An initial study by professor and climate researcher Masahiro Sugiyama suggests that people in the Global South may be more ambivalent or supportive than their northern counterparts, but it’s too early to say anything conclusive. Right now in the debate over geoengineering, it seems like the Global South exists mostly as an emotive tool to be wielded by proponents and detractors. The billions of people whose lives are at stake seem little more than an abstraction to both sides.

David Keith points out that most organizations opposed to geoengineering, like the ETC Group, are founded in the U.S. “They’re an environmental group but I think the fairest thing to call them is an anti-technology group,” he said. Along with opposing geoengineering, the ETC Group also ideologically opposes the spreading of industrial agriculture—instead, they support what they call the ‘Peasant Food Web’ (the amalgamation of all small-scale food production). It’s a position that Keith calls “morally monstrous,” since in his opinion, stopping industrial agriculture at this point in time would cause mass famines. 

On the flipside, the Solar Geoengineering Research Project that Keith belongs to is not funded by any fossil fuel-associated foundation (at least as far as its website discloses). Though some of their donors have securities in oil, other donors have missions that explicitly seek to reduce oil consumption. Despite this, Keith says that he’s often been accused of being funded by the oil lobby. For her part, Silvia Ribeiro of the ETC Group is quick to point out that Keith is part of a current geoengineering research effort that primarily exists in the West. “As history clearly and abundantly shows, a country like the U.S.A.—that currently is the place where most geoengineering research is conducted and where Keith works and gets funding for his solar geoengineering projects and experiments—will have little or no doubts [about] restrain[ing] itself from taking actions that could harm other countries,” she said. 

What should we make of all this back-and-forth sniping? It’s hard to say, but one thing is clear: before states have even had a chance to fight over the global thermostat, people and organizations are already struggling against each other today. Their concerns for the Global South’s welfare, no matter how accurate or well-meaning, are relatively uninformed by those people’s actual insights or lived experiences. 

Whatever the eventual decision on geoengineering, climate change reminds us of the fragility of our interconnected natural systems and the need to proceed with caution. In a debate without precedent, who gets the final say on bad weather? And will they regret their position if scientists don’t end up being the ones who captain the ship?