Cooling Earth's climate with commercial aircraft may be possible

As the global community scrambles to limit warming, a new study offers an unexpected possibility: we may not need to wait for advanced aircraft technology to intervene in cooling Earth’s climate.

In the face of growing concerns over climate tipping points and the slow pace of emissions cuts, some scientists have turned their attention to solar geo-engineering. This approach involves reflecting a portion of the Sun’s energy back into space to cool the planet.

Specialized aircraft may not be necessary

One proposed method is stratospheric aerosol injection (SAI), where sulphur dioxide is released into the upper atmosphere. There, it forms reflective particles that scatter sunlight and reduce global temperatures.

Until now, most models and strategies focused on injecting these particles high above the tropics – 20 kilometers or more – requiring specialized aircraft not yet in existence.

However, new research led by University College London (UCL) suggests a different, perhaps more accessible path: use commercial aircraft to inject particles at lower altitudes over the polar regions.

Cooling Earth with commercial aircraft

In the new study, the research team used 41 computer simulations with the UK Earth System Model to explore the effects of SAI at various altitudes, latitudes, and seasons.

The results showed that even at 13 kilometers (about 8 miles) – within reach of existing planes like the Boeing 777F – SAI could still cool the planet, though less efficiently than tropical high-altitude deployments.

“Solar geoengineering comes with serious risks and much more research is needed to understand its impacts. However, our study suggests that it is easier to cool the planet with this particular intervention than we thought,” noted lead author Alistair Duffey, a PhD student at UCL.

“This has implications for how quickly stratospheric aerosol injection could be started and by who.”

This approach would use lower altitudes over the poles because the stratosphere sits closer to the surface there. While the strategy achieves only about 35% of the forcing efficiency of traditional high-altitude methods, it still results in meaningful cooling and avoids the decade-long wait to develop custom aircraft.

How polar injection works

To reflect enough sunlight, aerosols must remain in the stratosphere where they are dry and stable, free from clouds that wash particles away.

The tropopause – the boundary between the troposphere and stratosphere – is lower at the poles. That allows existing jets to reach the stratosphere more easily at high latitudes than at the equator.

The simulations show that injecting 12 million tonnes (about 13.2 million US tons) of sulphur dioxide per year at 13 kilometers (about 8 miles) above 60° North and South could cool the Earth by about 0.6°C (about 1.1°F).

This is comparable to the cooling observed after the Mount Pinatubo volcanic eruption in 1991, which had a significant but temporary impact on global temperatures.

However, at 13 kilometers, aerosols linger in the atmosphere for months rather than years. This means more frequent injections would be needed to sustain cooling. In comparison, particles released at 20 kilometers can persist much longer, providing greater efficiency for the same mass of injected material.

The timing of aircraft injection

One of the most striking insights from the study is how the timing of aircraft injection matters for cooling Earth. Seasonal deployment, specifically during local spring and summer, improved both the conversion of sulphur dioxide into sulphuric acid and the lifetime of the particles.

These improvements occur because ultraviolet radiation – needed to drive chemical reactions – is more intense in the summer months, especially near the poles.

In fact, the study found that seasonal injection during spring and summer resulted in 39% more effective cooling than injecting year-round at the same altitude. This strategy produced more aerosol during the sunny months and avoided wasted effort during the dark polar winter, when particles would have little cooling effect.

The polar summer also reduces the longwave warming effect from larger particles, which tends to offset some of the cooling benefits of SAI. By optimizing timing, the low-altitude strategy compensates slightly for its reduced efficiency.

Benefits of using commercial aircraft

Deploying SAI using existing jets offers one major benefit: speed. Designing, building, and certifying high-altitude aircraft could take a decade and billions of dollars. In contrast, modifying current commercial planes could begin in just a few years.

“Although pre-existing aircraft would still require a substantial modification program to be able to function as deployment tankers, this route would be much quicker than designing a novel high-flying aircraft,” noted study co-author Wake Smith, Lecturer at Yale University.

The Boeing 777F, for example, could be adapted to carry and release sulphur dioxide at the necessary altitude. With a payload of over 100 tonnes (about 110 US tons) and an average of 5.7 flights per day, a fleet of 102 aircraft could deliver the required 21 million tonnes (about 23.1 million US tons) per year for 1°C (about 1.8°F) of cooling.

This would be more efficient than a larger fleet of smaller, custom-built high-altitude aircraft.

Practical and ethical challenges remain

Despite its potential, low-altitude polar SAI presents serious challenges. The efficiency trade-off means more sulphur dioxide must be injected to achieve the same temperature drop. That increases side effects such as acid rain, changes in ozone chemistry, and health impacts due to particle deposition.

Infrastructure also limits feasibility. While several northern airfields exist at high latitudes, options in the Southern Hemisphere are scarce.

For example, Ushuaia in Argentina is the southernmost large airport, but it handles fewer than ten flights a day. Major SAI operations would require new infrastructure in southern Patagonia or significant aircraft travel from lower latitudes, reducing efficiency and increasing costs.

Moreover, unequal cooling across the globe could worsen climate justice concerns. High-latitude injection cools the poles more effectively than the tropics.

That’s a problem because many of the world’s most vulnerable populations live in tropical regions, where the risks of heat, disease, and crop failure are already high.

Injections won’t replace emissions cuts

While low-altitude SAI could offer a stopgap solution, it does not eliminate the need to cut emissions. The researchers stress that this approach is not a replacement for long-term climate mitigation.

“Stratospheric aerosol injection is certainly not a replacement for greenhouse gas emission reductions as any potential negative side effects increase with the amount of cooling: we can only achieve long-term climate stability with net zero,” noted co-author Dr. Matthew Henry from the University of Exeter.

In addition to reducing emissions, any SAI strategy must roll out gradually to prevent sudden shifts in global temperatures. Abrupt cooling or rapid withdrawal could cause disruptions to agriculture, ecosystems, and human health. The risks of so-called “termination shock” remain a significant concern.

Looking ahead: A risky opportunity

This study expands the boundaries of what might be possible in near-term geoengineering. It introduces a technically feasible strategy that could be deployed using planes that already exist.

However, the approach is far from optimal. It is less efficient, comes with greater side effects, and offers uneven global benefits.

Still, the idea of using current aircraft for cooling Earth – even if modestly – adds a new dimension to climate policy. It highlights the importance of further research, not just to confirm technical viability, but to understand the social, ethical, and environmental consequences.

Whether low-altitude SAI becomes part of the global climate toolkit depends on decisions yet to be made. But this study opens that conversation with clarity, urgency, and a firm grounding in data.

It calls on policymakers to weigh aircraft-based cooling options carefully, and on scientists to keep exploring the boundaries of what is possible.

The study is published in the journal Earth’s Future.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–