Scientists have long explored the idea of cooling the Earth by reflecting sunlight back into space.
One possible method, called stratospheric aerosol injection, involves spraying tiny particles into the upper atmosphere.
These particles, like those released by a volcanic eruption, reflect sunlight and help lower global temperatures.
Until now, experts believed this could only be done effectively near the equator using specially designed aircraft capable of flying extremely high—up to 20 kilometers.
But a new study suggests we may not need such specialized planes after all.
Researchers from University College London (UCL), along with colleagues from Yale and the University of Exeter, found that existing commercial aircraft could potentially be used to deploy aerosols at lower altitudes over the polar regions.
Their study, published in the journal Earth’s Future, used computer simulations to test different strategies for deploying sulfur dioxide, which forms the reflective particles in the atmosphere.
According to their findings, injecting the particles at 13 kilometers above the poles—an altitude reachable by planes like the Boeing 777 freighter—could still cool the planet.
While this method would be less effective than injecting aerosols at higher altitudes in the tropics, it could still reduce global temperatures by about 0.6°C, a noticeable amount.
That’s about the same cooling effect that occurred after the 1991 eruption of Mount Pinatubo, which spread particles into the stratosphere and temporarily lowered global temperatures.
However, the polar strategy has trade-offs. Because the particles wouldn’t stay in the stratosphere as long, three times as much sulfur dioxide would be needed to have the same effect, increasing risks such as acid rain.
It would also be less helpful in tropical regions, which are particularly vulnerable to warming.
Despite the downsides, the researchers see this approach as a potentially faster and more affordable option.
Designing and building new high-altitude aircraft could take ten years and cost billions. Modifying existing planes could happen much sooner, offering policymakers a possible short-term tool while longer-term solutions are developed.
Still, scientists warn that stratospheric aerosol injection is not a silver bullet. It would need to be introduced slowly and carefully, and it wouldn’t replace the urgent need to reduce greenhouse gas emissions. Dr. Matthew Henry from the University of Exeter emphasized that while this method might help manage some climate impacts, lasting climate stability can only come from reaching net-zero emissions.
The study offers new insight into how existing technology might be used to help cool the Earth—but also underlines that this kind of geoengineering would be a complex and risky step, not a simple fix.
