Ordinary passenger jets flying over the poles while scattering sun-reflecting particles into the stratosphere might already be our best and most affordable tool for slowing an overheating planet

Passenger jets flying over the poles while scattering sun-reflecting particles into the stratosphere may already be our most affordable tool for cooling an overheating planet.

For years, the leading plan for seeding the stratosphere with sun-reflecting particles rested on a significant assumption: it would require a new generation of purpose-built aircraft capable of cruising at altitudes most jets never reach.

A modelling study led by researchers at University College London now challenges that premise. It suggests that existing commercial planes — the kind already operating on runways worldwide — may be capable of deploying stratospheric aerosol injection, a technique designed to slow planetary warming by bouncing a fraction of incoming sunlight back into space.

It has shaped assumptions about when solar geoengineering could realistically begin and, critically, which countries or actors would have the resources to pursue it.

The assumption that held geoengineering back

Most previous research on stratospheric aerosol injection started from the same point: to work, particles would need to be released in the tropics, at altitudes of 20 km or higher. That’s well above the cruising ceiling of any aircraft currently in commercial service.

No such plane exists yet. Getting one built, tested, and certified would be an enormous undertaking — an earlier study cited by the UCL team estimated that designing and certifying a purpose-built high-altitude aircraft could take a decade and cost several billion dollars.

That timeline matters. It has shaped assumptions about when solar geoengineering could realistically begin and, critically, which countries or actors would have the resources to pursue it.

What the new study actually found

The UCL-led team took a different approach. Rather than assuming tropical, high-altitude deployment, they ran simulations using the UK Earth System Model 1 (UKESM1), testing aerosol injection across a range of altitudes, latitudes, and seasons.

Their central finding: injecting sulphur dioxide at just 13 km altitude — near the polar regions, at roughly 60 degrees north and south — can meaningfully cool the planet. That altitude is already within reach of large commercial freighters. The Boeing 777F, for example, can operate at that height.

The study was published in the journal Earth’s Future. Lead author Alistair Duffey, a PhD student at UCL’s Department of Earth Sciences, described the finding as significant for understanding how quickly this intervention could realistically begin, and who could carry it out.

Why the poles — and why 13 km works there

The key is the structure of the atmosphere itself. The stratosphere — the dry, stable layer above most clouds — sits closer to Earth’s surface near the poles than near the equator, and that geographic fact is what makes lower-altitude injection viable in polar regions.

This distinction matters because aerosol particles behave very differently depending on which atmospheric layer they enter. In the troposphere, the lowermost layer, particles get swept into clouds and rained out within days. The stratosphere, being dry and cloud-free, allows them to persist for months.

At 20 km near the equator, particles can remain aloft for up to several years. At 13 km near the poles, that window shrinks to a few months — still, the simulations show persistence long enough to produce a measurable cooling effect. Timing also plays a role: injections timed to local spring and summer in each hemisphere maximize effectiveness, suggesting a seasonal deployment rhythm rather than year-round operations.

Trade-offs and side effects

The polar, low-altitude approach carries a significant efficiency penalty. According to the study, it’s roughly one-third as effective as high-altitude tropical injection, meaning approximately three times the aerosol volume would be needed to achieve the same temperature impact.

The simulations estimated that injecting 12 million tonnes of sulphur dioxide per year at 13 km could cool the planet by around 0.6°C — comparable to the temporary cooling observed after the 1991 eruption of Mount Pinatubo, a natural event that added a similar quantity of sulphur dioxide to the atmosphere.

Greater aerosol volumes bring greater side effects. Acid rain is one concern the researchers specifically flag. The approach also performs poorly in the tropics — the very regions where populations face the most direct exposure to climate-related heat, drought, and extreme weather. That geographic mismatch between where cooling is delivered and where it’s most needed is a meaningful limitation, not a minor footnote.

Not a fix — a tool that demands caution

The researchers are careful to frame their findings as informational, not prescriptive. Duffey emphasized that the study is about expanding the evidence base for policy-makers, not advocating for deployment.

Any real-world use of stratospheric aerosol injection would need to be introduced gradually. Sudden large-scale injection — or abrupt termination of an ongoing program — could trigger rapid temperature swings with potentially serious consequences. Risks remain incompletely understood.

Co-author Dr. Matthew Henry of the University of Exeter was direct: SAI can’t substitute for cutting emissions. “We can only achieve long-term climate stability with net zero,” he said. Co-author Wake Smith of Yale School of the Environment added that while modifying existing aircraft would still require a substantial program, it would be far faster than engineering a new high-altitude plane from scratch.

The finding that ordinary commercial jets could, in principle, already serve as delivery vehicles shifts the governance calculus considerably. If deployment no longer requires a decade of aircraft development, the question of who might act — and under what international framework — becomes considerably more urgent.

That’s perhaps the most sobering implication of this research. The science may be moving faster than the institutions designed to oversee it.

The study offers a more complete review: Alistair Duffey, Matthew Henry, Wake Smith, Michel Tsamados, Peter J. Irvine. Low‐Altitude High‐Latitude Stratospheric Aerosol Injection Is Feasible With Existing Aircraft. Earth’s Future, 2025; 13 (4) DOI: 10.1029/2024EF005567

Daniel Garcia

Daniel García is an Editor-in-Chief with strong expertise in structural work and engineering principles. He combines this technical foundation with deep knowledge of energy, spatial design, and emerging technologies, bringing a forward-thinking and analytical approach to editorial leadership.