From the devastation wrought by recent extreme weather events to the dismal climate warnings issued last week by the Intergovernmental Panel on Climate Change, urgency around climate action is mounting. That urgency has increased some of the buzz around geoengineering, or the deliberate large-scale technical interference in Earth’s climate system. At this point, the discussion is largely theoretical. But as it gets more pointed and specific, it also raises a host of ethical questions. Many scientists and ethicists caution that the side effects of such intervention could be just as bad, if not worse, than the original problem. One study, for instance, suggests that efforts to mitigate hurricane intensity in the Northern Hemisphere could enhance tropical cyclone activity in the Southern Hemisphere. Another study suggests that similar efforts to reduce warming could exacerbate drought in some regions. For many ethicists, however, the question of whether or not we should intentionally geoengineer the planet hinges on how desperate the problem becomes. As one environmental sociologist puts it: “There might be a scenario in which solar geoengineering is better than not having it. I really hope we never have to face that choice.”

The idea of blotting out the sun, whether floated by Frédéric Bastiat or Montgomery Burns, has long stood as a metaphor for human arrogance.

But today, as the planet approaches critical temperature thresholds, some observers are now saying that reducing the amount of sunlight, and therefore heat, that reaches the Earth’s surface, is not just technologically feasible, but also necessary to avoid catastrophe.

The latest report from the United Nations’ Intergovernmental Panel on Climate Change, with its warnings of worsening water shortages, heat waves, and rising seas, along with the catastrophic damages from extreme weather events like hurricanes Michael and Florence, have increased some of the buzz around geoengineering: deliberate large-scale technical interference into the Earth’s climate system.

At this point, the discussion is largely theoretical. But as it gets more pointed and specific, it also raises a host of ethical questions. Nearly every weather event, from a tornado to a windless day, produces winners and losers. But what happens when those winners and losers arise from deliberate policies?

“Is this a problem that’s so new that we have to come up with completely new ethical tools to even understand it?” asks Forrest Clingerman, professor of religion and philosophy at Ohio Northern University and co-editor of the 2016 book, “Theological and Ethical Perspectives on Climate Engineering.” “Is this a technology that raises similar questions ethically as some other technologies that we’ve seen in the past,” he asks. “Or is this fundamentally new?”

The most common form of geoengineering that gets discussed is stratospheric aerosol injection, which would use artillery or aircraft to deposit reflective particles into the upper atmosphere, about 12 miles up. These particles – scientists have proposed everything from sulfur dioxide to calcium carbonate to even diamonds – would either directly or indirectly redirect a portion of the sunlight striking them back into space. In theory, this additional reflectivity would make the surface below a little cooler than it otherwise would be: enveloping the planet in a giant reflective veil.

But that sort of solar geoengineering intentionally creates a layer of pollution in the atmosphere, and is also likely to cause climate problems in certain places, such as drought in the tropics. And it doesn’t address the fundamental underlying problem of too much carbon dioxide in the atmosphere.

Scientists have also floated other ideas, from building a giant, space-based sunshade to fertilizing the oceans with iron to promote plankton growth. And at a far more accepted – and less theoretical – level, some forms of carbon removal technologies are also a form of geoengineering. Carbon removal has fewer ethical pitfalls, however, and as it has become a bigger part of the discussion, the geoengineering label has largely been dropped.

Scientists who think such tools at least warrant investigation note that humans are already playing a massive role in the Earth’s climate, albeit unintentionally.

“There’s a strain in environmentalism that doesn’t want humans to interfere in nature, which is something I understand and empathize with,” says Holly Jean Buck, a fellow at the Institute of the Environment and Sustainability at the University of California, Los Angeles. “The problem is, though, that we already have to such a degree that some degree of repair and restoration is needed.”

In search of the greatest good

Trying to affect weather patterns, at least at a local scale, isn’t terribly new. Cloud seeding to mitigate drought has been used for more than 75 years. And back in 1947, the US military attempted to break up a hurricane that was stalled off Florida’s coast, by dumping dry ice into the clouds. The day after a pilot did just that, the hurricane changed direction and hit the Georgia coast. It’s still unclear whether the dry ice precipitated the change in direction, but the public blamed the government, and Project Cirrus, as it was called, was canceled.

Today, discussion of large-scale, whole-planet climate manipulation brings up the same questions of winners and losers. A 2017 paper published in the journal Nature Communications suggests that stratospheric aerosol injection could potentially mitigate hurricane activity – but that if it was applied in the Northern Hemisphere, it might enhance tropical cyclone activity in the Southern Hemisphere, and vice versa.

“We’ve been unintentionally geoengineering for centuries. But there does seem to be something fundamentally different between accidentally doing something and saying, ‘OK, now we’re going to intentionally do this,’ “ says Professor Clingerman. “Climate change generally speaking is something that is global. And it’s also intergenerational. That complicates any utilitarian calculus.”

But others say that we may get to a point where there’s little choice, and where the ethical consideration is what produces the greatest good for the greatest number of people.

“Utilitarianism is probably the only plausible approach to thinking about it,” says Martin Bunzl, a philosophy of science professor at Rutgers University and director of the Initiative on Climate and Social Policy.

Professor Bunzl says the bigger concerns he has are with the uncertainties. It’s impossible to experiment in a small way with large-scale geoengineering, so scientists would have to rely on computer modeling and hypotheses, without any controlled rigorous testing.

“Even if you do it at a global level and, say, ramp up the dosage to try and see the effects, it would take far far too long to distinguish between noise and signal,” says Bunzl. “So you’re really put in the position of having to go to something like full insertion.”

But he says he thinks it may well get to the point where we’ve failed at other climate mitigation strategies and the risks of geoengineering seem worth it. And, if computer modeling significantly improves over the next few decades, it could allow us to have a more informed discussion about just what those risks are.

“I think that would strongly affect the way this debate has gone, because a lot of this debate has less been on the ethics of one particular population bearing the cost of this, but on the unknowns about the effects,” Bunzl says.

At this point, the discussion of solar geoengineering is still pretty theoretical, with scientists just beginning to have a handle on how it might work, as well as how it would affect complex weather and atmospheric patterns.

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But as climate impacts are increasingly felt, its place in the international debate is growing.

“There’s no question that solar geoengineering is a terrifying prospect. It involves changing the amount and type of sunlight coming down to the whole Earth,” says Dr. Buck. “There’s not another Earth where you could do it differently and see what happens, or see what happens in the absence of it.... But the fact of the matter is that maybe there’s a scenario where climate change is causing mass suffering and perhaps playing a factor in conflicts. There might be a scenario in which solar geoengineering is better than not having it. I really hope we never have to face that choice.”