Climate change is the most immediate existential threat we are currently facing. The challenge of tackling climate change before it is too late is enormous and seems in many ways almost intractable given current policies and humanity’s poor track record for cooperating on a truly global scale.

These are desperate times, which may call for desperate measures. For instance, an extreme solution that has been previously proposed is injecting microscopic aerosol particles into the upper atmosphere that reflect incoming sunlight back into space, thereby resulting in a net cooling effect. It’s the same mechanism that explains why the global climate cools down following a major volcanic eruption.

Now, in a new study, researchers at Yale University have proposed a more actionable geoengineering plan that involves injecting aerosols at latitudes of 60 degrees both north and south. This approximately lines up with Anchorage, Alaska in the north and the tip of Patagonia in the south. These heat-blocking particles would swiftly travel poleward, driven by currents, where they would shade the now melting surface below, cooling it by as much as 2°C. So essentially, geoengineering is all about dimming the sun.

Importantly, the researchers also crunched the numbers financially speaking, estimating this kind of intervention would cost around $11 billion. This investment would be required yearly as the aerosols would have to be replenished. That sounds like a lot of money, but that’s only a tiny fraction of the $125 trillion required to meet net zero by 2050, the UN says.

“There is widespread and sensible trepidation about deploying aerosols to cool the planet,” notes lead author Wake Smith, a lecturer at Yale University and a Senior Fellow at the Mossavar-Rahmani Center for Business and Government at the Harvard Kennedy School,“but if the risk/benefit equation were to pay off anywhere, it would be at the poles.”

The operation would be performed by enormous tanker airplanes that don’t yet exist at altitudes exceeding 13,000 meters (43,000 feet), which would dump copious amounts of sulfur dioxide. The plan entails releasing as much as 6.7 billion kilograms of sulfur dioxide at each pole. As the sulfur dioxide moves into the stratosphere, it would combine with water to form sulfuric acid aerosols. The sulfuric acid would make a haze of tiny droplets to reflect incoming solar radiation, causing cooling of the Earth’s surface.

These aerosols can stay in the stratosphere for up to three years, moved around by winds and resulting in significant cooling worldwide. Eventually, the droplets grow large enough to fall to Earth, so a new stock of aerosols has to be sprayed yearly by a fleet of more than 100 super-heavyweight airborne tankers, similar in design to the military tankers that provide air-to-air refueling. Alternatively, giant balloons tethered to a maritime tanker through a 20-kilometer-long flexible pipe could perform the job, as previously proposed by the SPICE Project, which stands for stratospheric particle injection for climate engineering.

A controversial solution

It’s painfully obvious how geoengineering the planet can backfire. Even a well-crafted plan is risky because even if there’s a 1% chance that something goes wrong, the consequences are global.

Geoengineering, which has been described as a ‘techno-utopian dream’, does nothing to address the underlying cause of climate change. In many ways, it’s just sweeping the dirt under the rug, with the promise of buying time until we can perform the necessary investments to decarbonize the planet.

On paper, geoengineering has its merits, but the risks are significant. Injecting sulfate aerosols in the stratosphere above the Arctic to mimic volcano clouds, could potentially disrupt the monsoons in Asia and increase droughts, particularly in Africa, endangering food and water security for nearly two billion people, according to Silvia Ribeiro, the Latin America Director for ETC group. Even the researchers themselves aren’t firm supporters of geoengineering, seeing it more as a last course of action that we might be forced to undertake in the future.

“Game-changing though this could be in a rapidly warming world, stratospheric aerosol injections merely treat a symptom of climate change but not the underlying disease. It’s aspirin, not penicillin. It’s not a substitute for decarbonization,” says Smith.

There are also major geopolitical concerns. It’s easy to imagine how some governments would see altering the global climate, thereby potentially driving storms, droughts, and all manner of calamities within their borders, as an act of war. For this reason, it is unlikely that geoengineering at a global scale will ever be allowed, although some countries like China have rather extensive weather-modification programs that artificially enhance rain, which could cover 60% of the country by 2025. Elsewhere, Australia is testing marine cloud brightening to cool the water in the Great Barrier Reef, which is currently under great distress, having lost more than half of its coral population in the last three decades.

According to the researchers, their proposed plan is designed to limit climate-altering effects to the poles, where less than 1% of the global human population lives.

“Nonetheless, any intentional turning of the global thermostat would be of common interest to all of humanity and not merely the province of Arctic and Patagonian nations,” adds Smith. For instance, by preventing the melting of glaciers and ice sheets, geoengineering could stave off sea levels rise that is now threatening hundreds of millions of people living in coastal regions.

However, if the world agreed to undertake such a risky action, the method is not devoid of its challenges. The infrastructure required to inject that many aerosols on a regular basis are immense. By the authors’ estimates, more than a hundred sorties per hour would have to be undertaken for months. We’d need new sulfur dioxide factories and the supply chain infrastructure that comes with it. All of this could take at least 15 years and would ironically most likely involve the production of a lot of CO2, which would exacerbate the very problem that geoengineering is supposed to address.

When debating geoengineering, there are no easy questions and answers. But for now, it’s a topic worth exploring. Hopefully, we might never be forced to turn to geoengineering, but it’s good to have the option on the table if things really heat up. After all, we need all the help we can get.

The findings appeared in the journal Environmental Research Communications.