Is geoengineering becoming a “respectable” idea, as The Economist claimed two years ago? The large-scale climate alteration—akin to "restarting" the Earth system, like rebooting a computer overwhelmed by heat—is one of the most extreme responses proposed to address global warming.
Interest in a wide range of technologies (the term "geoengineering" is used as an umbrella) has grown steadily since climatologists began acknowledging that the situation is worse than predicted by models. 2023 and 2024 were the hottest years ever recorded, and 2025 has not started off well. Moreover, the more ambitious climate goals set ten years ago—such as limiting global temperature increases to 1.5°C above pre-industrial levels—now appear increasingly out of reach.
Even James Hansen, often referred to as the father of climate science and former head of NASA’s climate study centre, has argued for years that geoengineering could be one of the last options available to avoid the worst effects of the climate crisis. He stresses that, given the situation, we cannot dismiss it outright.
Geoengineering could be described as the “temptation of the skies”. It is an emerging field that is attracting increasing investment and attention, yet it carries unforeseen ecological and geopolitical risks. Public research in this area is steadily growing; the U.S. National Oceanic and Atmospheric Administration (NOAA) has invested $22 million in a new project, the Earth's Radiation Budget Initiative, while the UK's Advanced Research and Invention Agency (ARIA) has committed £56 million to a similar initiative. Even Harvard's Solar Geoengineering Research Program is drawing growing public and private funding to support studies in this area.
Alongside academic research, an increasing number of startups are emerging in the private sector, aiming to amass resources, techniques, and patents related to climate change. Among them, the most talked-about—partly due to a series of unscrupulous actions in recent years—is the American company Make Sunsets. In 2023, it conducted a pirate experiment to alter the weather in Mexico. Following that episode, the government of Mexico banned geoengineering experiments.
But first we need to understand what we mean by 'geoengineering'.
This sector is divided into two major branches. The first, which is both the most dangerous and the most ambitious, is solar radiation management (SRM). These techniques vary, but they all aim to modify the Earth's albedo—its ability to absorb heat. The goal is to reflect part of the sunlight back into space, rapidly cooling the planet. The second field is CO₂ removal (Carbon Dioxide Removal, CDR). These are strategies and technologies designed to remove carbon from the atmosphere. Though it carries fewer risks, it also has less potential for impact.
In the first case, this involves the injection of stratospheric aerosols to create a reflective shield against the sun, replicating the cooling effect similar to that after a large volcanic eruption. Research institutes are also exploring other methods, such as brightening sea clouds by spraying saltwater to increase their albedo, or even using orbital mirrors or reflective surfaces. However, these remain theoretical proposals. The second category includes direct air capture, industrial plants that aspirate CO₂, as well as ocean fertilization projects—more natural methods but with a slow and limited impact.
The main risk is systemic: the atmosphere is a complex and interconnected system, of which our understanding remains partial. Altering it in one place could create imbalances elsewhere. SRM technologies, for example, could reduce rainfall in specific regions of Africa, alter monsoons in Asia, and damage the ozone layer.
Furthermore, there is a governance issue: no organizations currently regulate these operations, and it is difficult to envision the creation of a new entity, especially when multilateralism is facing such challenges. There is a real risk of increasing geopolitical conflicts, as evidenced by the tensions resulting from the Make Sunsets incident in Mexico.
There is also the problem of the so-called “termination shock”: what would happen if a Solar Radiation Management project were suddenly suspended or abandoned by a company or a government? Such an event could trigger the opposite effect: a sudden and devastating temperature surge.
Finally, many scientists fear that geoengineering may represent a dangerous false solution. It could divert us from the primary way to address the climate crisis: reducing greenhouse gas emissions. By creating the illusion that our energy systems can continue as usual, geoengineering may lead us to believe we've found a "magic wand" to control the Earth's climate.
In short, geoengineering is still an untested solution at a large scale, as it has only been explored in prototype or theoretical form. One of its applications could be the emergency brake of global warming, but it may also cause unforeseen and potentially more serious problems than the ones we face now.
The debate must be approached with objectivity, and we must be aware of both risks and opportunities, focusing on research rather than fear. For such interventions, we certainly need more data and information, along with greater democracy and public participation in decisions that will shape the future of humanity.