CLIMATEWIRE | A futuristic geoengineering proposal might be easier to accomplish in the real world than scientists previously thought.
New research suggests that a planet-cooling strategy known as solar radiation management is already possible with existing commercial airplanes. Until now, many experts suggested the technology probably would require specialized high-altitude aircraft. And assembling a large enough fleet of these machines could take a decade or more.
The new study, published Monday in the scientific journal Earth’s Future, makes the case that solar geoengineering — currently a hypothetical strategy — could overcome the vehicle hurdle without a major technological leap.
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But the concept remains deeply controversial among both scientists and climate activists. And the new study’s authors cautioned the strategy needs more study before world leaders move forward.
“We need to know more, we need to do more research,” said lead study author Alistair Duffey, a Ph.D. student at University College London, in an interview with POLITICO’s E&E News. “There are huge risks and huge uncertainties that require a concerted effort from the research community to tackle before it would make sense to have any kind of opinion about doing this in the real world.”
Most climate experts agree that solar geoengineering is not a substitute for reducing emissions, he added. Phasing out fossil fuels and curbing greenhouse gases remain the primary strategies for tackling climate change.
Even so, solar geoengineering is gaining global attention — from both advocates and critics — as Earth’s temperatures continue to rise.
World leaders so far have failed to curb greenhouse gases at the speed necessary to align with the Paris Agreement’s international climate goals. Some advocates argue that geoengineering eventually could become a necessary strategy to cool the planet, and that researchers must keep studying its potential.
But other experts warn that too much focus on geoengineering could distract world leaders from their progress on reducing emissions. And some worry that it could increase the risk of a country or company going rogue and attempting a large-scale geoengineering project without global cooperation.
The new study doesn’t make any arguments for or against geoengineering as a climate intervention. Instead, it explores scientific questions related to the technology the project would require — if it ever got to that stage.
The most commonly discussed form of geoengineering hinges on a strategy known as solar aerosol injection — spraying reflecting particles into the atmosphere to beam sunlight away from the planet. Previous studies have suggested this strategy would work best at very high altitudes, where the particles have the longest lifetime in the atmosphere. At lower altitudes, they’re less effective and fall out of the air faster.
Research suggests the most effective height for particle spraying is around 12.5 miles above the surface of the Earth. But most existing aircraft can’t safely fly at that altitude. That means any future large-scale geoengineering operation would require a fleet of specially designed planes, which could take years to develop.
But the new study suggests effective geoengineering still could be possible at lower altitudes.
Using a computer model designed to simulate the Earth system, Duffey and his colleagues ran a series of experiments comparing the effects of aerosol injections at different altitudes, latitudes and times of the year.
They found that conditions for low-altitude particle spraying were most favorable closer to the Earth’s poles, where the shape and thickness of the Earth’s atmosphere is slightly different than it is closer to the equator. They also found that spring and summer were the best seasons, when there’s more sunlight for the particles to reflect.
These experiments were still far less efficient than high-altitude injections, the study noted. In fact, they’re only about 35 percent as effective as similar projects conducted at the recommended 12.5 miles high in the subtropics.
But they still could make a meaningful dent in the Earth’s temperatures at just 8 miles above the surface of the Earth — a height that’s safe for many commercial aircraft.
The simulations found that spraying 12 million metric tons of reflective sulfur dioxide into the atmosphere at 8 miles altitude and 60 degrees latitude in the spring and summer would result in about 0.6 degree Celsius, or 1.08 degrees Fahrenheit, of global cooling.
The concept still needs more research, though, the study authors cautioned.
Particles in the atmosphere tend to diffuse more quickly from east to west than they do from north to south, meaning the immediate effects of solar geoengineering deployed at high latitudes might be stronger at the poles than at the equator. In theory, that could be useful for purposes like refreezing sea ice or slowing the melting of the world’s ice sheets.
But many of the countries most vulnerable to the impacts of climate change are located in the tropics, the authors noted. If world leaders one day consider geoengineering for the good of the planet, a polar injection strategy might mean that regions closer to the equator wouldn’t benefit as strongly.
At the same time, a low-altitude injection strategy, with particles sprayed closer to the surface of the Earth, could carry the risk of stronger, unintended side effects. Some studies have suggested that solar geoengineering could have unwanted impacts on the Earth’s ozone layer or precipitation patterns, and those potential consequences still need more research.
The team hopes to address some of these questions in future studies, Duffey suggested.
For now, the new research adds another data point to help answer scientific questions about the potential risks and benefits of geoengineering.
“It doesn’t avoid the need for climate action,” Duffey cautioned, noting that reducing carbon emissions is still the most important strategy for addressing climate change.
“It would be very, very scary, very risky, to be living in a world that just offsets more and more of the greenhouse-gas-forced warming with more and more reflecting of sunlight,” he said. “That’s not a world we want to live in.”
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2025. E&E News provides essential news for energy and environment professionals.