Imagine a morning sometime in 2045. You step out onto your balcony in Buenos Aires, and the sky over the Río de la Plata has a strange, milky hue – not fog, not smog, but something in between. The sun is shining, but as if through frosted glass. The temperature is three degrees lower than it should be for the season. Somewhere in the stratosphere, twenty kilometers up, particles of sulfur aerosols are slowly settling – a man-made cloud reflecting sunlight back into space. This is not an accident. This is the plan.
This is what one of the most ambitious and controversial projects in human history might look like: geoengineering. A deliberate, large-scale intervention in the planet's climate systems to slow or reverse global warming. An idea that sounded like science fiction just twenty years ago is now being discussed in serious academic journals, funded by major foundations, and sitting on the tables of climate organizations.
The future is best seen in the details. And those details are already here.
What is geoengineering, and why are we talking about it now?
Geoengineering isn't a single technology but a whole family of approaches united by a common idea: if we can't cut carbon dioxide emissions fast enough, we could try to change how the Earth responds to them. Roughly speaking, not treating the disease, but managing the symptoms. Or, in a more optimistic reading, buying time while the world rebuilds its energy infrastructure.
The interest in this topic didn't come out of nowhere. Average global temperatures continue to creep upward. International agreements to reduce emissions are being implemented more slowly than hoped. The Arctic is melting, coral reefs are bleaching, and extreme weather events are becoming more frequent. Against this backdrop, a temptation has emerged for some in the scientific and political communities: what if there's a faster way?
Geoengineering approaches are typically divided into two broad classes. The first is Solar Radiation Management (SRM): methods aimed at reflecting some of the sun's light back into space to cool the planet. The second is Carbon Dioxide Removal (CDR): technologies that pull CO2 from the air and either sequester it underground or use it in some other way.
Both classes are fundamentally different in their nature, their risks, and the reversibility of their consequences.
A Mirror in the Stratosphere: How Solar Radiation Management Works
The most discussed and, at the same time, most alarming method is stratospheric aerosol injection. The idea is simple: tiny particles – most often sulfur dioxide or calcium carbonate – are sprayed into the upper layers of the atmosphere. These particles scatter and reflect sunlight, reducing the amount of heat that reaches the Earth's surface.
Nature itself has shown us that this works. In 1991, the eruption of Mount Pinatubo in the Philippines released about twenty million tons of sulfur dioxide into the atmosphere. Over the next two years, the average global temperature dropped by about 0.5°C. The effect was noticeable everywhere, from crop yields to the color of sunsets. It was this observation that became the starting point for serious scientific interest in artificial aerosols.
Technically, this could be achieved in several ways: with specially designed aircraft, high-altitude balloons, or even artillery capable of launching aerosols to the required altitude. The cost of such operations, by various estimates, could be relatively low compared to other climate solutions – which in itself makes this method dangerously appealing.
Why dangerous? Because low cost and technical accessibility mean it could be done not just by an international consortium under UN control, but also by a single state, a large corporation, or even a wealthy private individual. In 2022, an American startup, Make Sunsets, launched several balloons with sulfur dioxide over Mexican territory without any approval from the country's authorities. Mexico responded by banning geoengineering experiments in its territory. A precedent was set: the technological barrier is so low that it has outpaced any regulation.
But the technical risks are even more serious. Stratospheric aerosols don't just cool the planet – they change precipitation patterns. Models show that reducing solar radiation could weaken the monsoons in South Asia and West Africa, cutting rainfall in regions where the agriculture of hundreds of millions of people depends on it. Some areas would benefit from the cooling; others would lose out to drought. And none of the affected parties would have consented to this experiment.
There's another detail, one that is less often discussed. Aerosols in the stratosphere are temporary – they need to be constantly replenished. If a spraying program were to be stopped abruptly – due to a political crisis, financial collapse, or any other disruption – temperatures would begin to rise at twice the speed, as the CO2 accumulated in the atmosphere wouldn't have gone anywhere. This effect is known as the termination shock, and it could be more catastrophic than the original warming it was intended to prevent.
Other Mirrors: Cloud Brightening and Marine Methods
Stratospheric aerosols are the most radical option for solar radiation management, but not the only one. A more localized approach is marine cloud brightening. The idea is to use special ships to spray seawater into low clouds over the ocean. The tiny salt droplets increase the clouds' brightness, causing them to reflect more sunlight and lowering the surface water temperature.
It sounds more delicate than stratospheric interventions: the impact is local, the effect more predictable, and the technology itself doesn't require working at dizzying heights. But here, too, there is no certainty about how regional climates would change if such operations were scaled up.
Ideas for ground-based albedo are also being studied – brightening the Earth's surface or the roofs of buildings to reflect more heat. Imagine if the roofs of all major cities were painted white – this would produce a noticeable, albeit modest, cooling effect. Argentine architects working with the hot climate of the Gran Chaco have long used this principle intuitively. The question is whether it can be applied widely enough to change the global picture.
CO₂ Removal: Treating the Cause, Not the Symptom
The second class of geoengineering technologies is considered safer, although significantly more laborious. The logic here is different: not to reflect heat, but to remove the very greenhouse gas that traps it from the atmosphere.
The most natural of these methods is reforestation and soil management. Trees absorb CO2 and store carbon in their biomass. Restoring degraded forests and changing agronomic practices – adding organic matter to the soil, reducing tillage – can gradually increase carbon stores in ecosystems. This path is slow and requires vast areas of land, but it doesn't carry catastrophic side effects.
A more technologically complex option is Direct Air Capture (DAC). Special facilities filter atmospheric air and chemically bind the carbon dioxide, which is then injected into deep geological formations or used in industry. Several such plants are already in operation – in Iceland, Canada, and the US. The one problem is cost. Currently, capturing one ton of CO2 via DAC costs hundreds of dollars, while the global economy emits about forty billion tons annually. The math doesn't add up yet.
There are also hybrid biological approaches. Bioenergy with Carbon Capture and Storage (BECCS) involves growing plants that absorb CO2 as they grow, then burning this biomass for energy and capturing the resulting carbon dioxide before it enters the atmosphere. In theory, it's a nearly carbon-neutral cycle. In practice, it requires colossal areas of agricultural land that compete with food production.
Another method is ocean iron fertilization. Marine phytoplankton absorb CO2 during photosynthesis, but their growth in some parts of the ocean is limited by an iron deficiency. The logic is simple: add iron, get more plankton, get more absorbed CO2. Experiments have been conducted since the 1990s with mixed results: the plankton does bloom, but a significant portion of the absorbed carbon returns to the atmosphere after the organisms die. Plus, the changes to the ocean's ecosystem are unpredictable and could affect fish stocks that coastal communities depend on.
Who Decides, and for Whom?
This is where the truly difficult part of the conversation begins. Because geoengineering is not just a technical choice. It is a choice about who has the right to interfere with the planet's climate system, whose interests are prioritized, and who bears the responsibility if something goes wrong.
Existing international agreements are not prepared for this. The Paris Agreement on climate change does not directly regulate geoengineering methods. The London Protocol on ocean dumping contains restrictions on ocean fertilization, but its application is inconsistent. There is no global body authorized to make decisions about stratospheric intervention.
This means the field is wide open. And players are already entering it.
Small nations, especially those vulnerable to sea-level rise and extreme heat, are showing a keen interest in SRM technologies: for them, it can look like the only available means of protection. Major powers tend to view geoengineering with suspicion – especially if an intervention is initiated without their consent. The scientific community is divided: some demand immediate research, while others insist on a moratorium until an international governance system is in place.
Latin America holds a special place in this conversation. The region, which possesses the world's largest tropical rainforest and is extremely vulnerable to changes in monsoon patterns and river flows, is simultaneously a potential beneficiary of cooling technologies and their potential victim. A change in precipitation patterns over the Amazon or the Pampas could have consequences for the agro-industrial sector comparable in scale to the largest economic crises.
A Scene Not Yet Staged, But Already in Rehearsal
Let's return to that morning on the balcony. The milky sky over Buenos Aires. The sun behind frosted glass. Three extra degrees of cold.
Who made this decision? A consortium of states? A body within the UN? Or a private company with a well-equipped fleet of high-altitude aircraft and a legal team skilled enough to operate in legal loopholes? Who held public hearings with the residents of the Chaco, whose agriculture depends on summer rains? Who explained to the fishermen of Patagonia that the change in water temperature is a side effect of global climate optimization?
It is precisely these questions that make geoengineering not just a scientific problem, but a deeply human one. Technology is always a neutral tool until someone decides who gets it and who pays the price.
Within the scientific community, a position is gaining traction that can be summarized as follows: research is necessary, but deployment should only happen with international governance and the principle of consent. This means: running climate models, conducting small, controlled experiments, developing protocols – but not deploying full-scale operations until a structure capable of being held responsible for them is in place.
It sounds reasonable. But the history of technology has seen many cases where the barrier between 'develop' and 'deploy' was nothing more than the speed of events.
What's Left Off-Screen
The quietest and perhaps most important question, one that is almost never heard in public discussions about geoengineering, is the question of moral hazard. If humanity knows it has an emergency lever – the ability to cool the planet by spraying aerosols into the stratosphere – will it try less hard to reduce emissions? Why go through the painful process of overhauling energy, transport, and industry if you can just push a button in a worst-case scenario?
This argument is particularly worrisome to those who have spent decades working on systemic changes in energy and land use. Geoengineering as an insurance policy could become an excuse for inaction. Its very existence changes the political psychology of climate negotiations.
On the other hand, there is a scenario in which this objection becomes a luxury. If warming by mid-century turns out to be significantly faster than predicted, if tipping points in the climate system are crossed sooner than expected, then the ability to intervene quickly may be the only thing separating a managed crisis from an unmanageable collapse. In this scenario, the question is not 'to do or not to do,' but 'who, how, and with whose consent?'
It is this shift in the framing of the question that is happening right now – slowly, in academic papers, working groups, and closed-door meetings. Geoengineering is moving from a forbidden idea to an undesirable but discussable one. The next step – from discussable to permissible – may be much shorter than we think.
The Details That Make Up Tomorrow
At a recent seminar on climate law in Buenos Aires, a young researcher from the University of Buenos Aires showed slides with maps of precipitation changes under various stratospheric intervention scenarios. In one scenario, the Pampas became significantly drier. The country's northeast, by contrast, received more water. The audience watched in silence. Then someone asked, 'But who will actually be making this decision?' There was no answer.
That silence is precisely the point we are at now. The technologies are mature enough to be dangerous. The regulatory framework can't keep up. The scientific understanding of the consequences remains incomplete. And all the while, the pressure of the climate crisis is mounting, creating the temptation to use what's available – right now, without waiting for consensus.
Geoengineering is a mirror humanity has held up to its own face. In it, we see not only the desire to fix what is broken, but also the habit of deciding for everyone, without asking. Both traits are ours. Both will matter.
